Nitrogen And Other Things

[TwoTankAmin]

Before going into any discussion I would like to suggest interested folks have a read at the link below. It could be written a bit clearer but it goes a long way towards explaining things in regards to testing for ammonia, nitrite and nitrate and what role nitrogen plays in it all. However, the reason for having this discussion is to gain a better insight into two areas relevant to the hobby. The first is how these compounds effect the cycling phase of setting up an established tank effectively and efficiently which mostly relates to the nitrifying bacteria. The second is how these compounds affect the fish and other critters and plants in tanks.

Before reading, please bear in mind this was last modified 02-Sep-1994. It is part of the Index Annex area of the FINS site. The fast link is http/fins.actwin.c...trate-tests.txt

To get there via the FINS site, go to their Aquria Facts page here http/fins.actwin.com/aquariafaq.html and click on Article Annex. Then click on nitrate-tests.txt.

One thing to bear in mind is that back then the scientific literature may have used different terms. But in the few hundred abstracts and papers I have read on related topics, I have almost always seen ammonia and nitrite readings stated as -nitrogen or -n. On the other hand it appears that most kits in hobby use are measuring ions.

 

[TwoTankAmin]

The questions to which this thread will hopefully supply some reasonable answers include:

What are your test kits really measuring and what do the results really mean?

What does the scientific literature say regarding the the potential toxicity to fish and other tank inhabitants from ammonia, nitrite and nitrate?
- What are the differences, if any. in the potential effects these things have on the bacteria vs the fish etc.?

Here are a few teaser questions:
- Why is ammonia (NH[sub]3[/sub]) so much more toxic to fish than ammonium (NH[sub]4[/sub][sup]+[/sup]).
- Which is more toxic to fish- ammonia or nitrite?
- I am cycling with fish and my test kit says I have .25 ppm of ammonia, what does this mean and what should I do?

 

[TwoTankAmin]

No takers? Come on surely at least one member out of the other 90,566 besides me must be willing to take a shot at answering any of the three teaser questions? I would hate to think that out of over 90,000 fish keepers nobody knows the answers.

 

[daizeUK]

I did attempt to research answers to these interesting questions but I got frustrated by the number of scientific papers that require registration or purchase to read beyond the first page. I can only give answers based on partial scientific abstracts and internet hearsay, but I can't cite reliable sources which is what I think you intended.

Well I will give you what I got anyway. It's not very good I'm afraid, the answers are either out of my head or from unreferenced sources, perhaps someone else can do better?

Why is ammonia (NH[sub]3[/sub]) so much more toxic to fish than ammonium (NH[sub]4[/sub][sup]+[/sup]).
Fish excrete ammonia as a waste product, primarily through their gills but also via their kidneys. Accumulated ammonia has a caustic effect on the surface of the gills and can cause internal and external bleeding, characterized by red gills and bloody patches on fins and body. The fish may become lethargic and lose appetite and might be seen gasping at the surface or lying still at the bottom of the tank with fins clasped.
Ammonium is also excreted through the gills, but indirectly via a more complicated chemical process which means that the gills are less permeable to ammonium ions and therefore less affected by external ammonium ion concentrations.

Which is more toxic to fish- ammonia or nitrite?
Off the top of my head, I know that nitrite is less toxic than ammonia (by a certain factor, about 5 if I recall correctly?), I can't find where I read that though!

I am cycling with fish and my test kit says I have .25 ppm of ammonia, what does this mean and what should I do?
An ammonia reading above zero indicates that ammonia nitrifying bacteria are not yet established well enough to cope with the bioload on the tank.
Any concentration of ammonia above zero is detrimental to fish and immediate steps should be taken to remove ammonia from the water. These include:

1) Replace between 25% and 50% of the water in the tank (some people will say 75% up to 95%, depending on who you ask!)
2) Add treatments to remove ammonia from the water
3) Lower the pH to convert ammonia in the water to non-toxic ammonium (discussion point: a pH change is known to shock the fish and could potentially kill them if they are already suffering from ammonia poisoning? So I'm not sure about this one.)
4) Reduce feeding fish (discussion point: reducing food makes sense to minimise uneaten food and to reduce ammonia production, however arguably not to the point of under-feeding the fish as there is evidence that well-fed fish are more resistant to ammonia poisoning due to a natural mechanism whereby they increase their resistance to ammonia while they are excreting it)

Perhaps it's equally important to consider where the ammonia is coming from and deal with the source as well as the symptoms. During cycling it is most likely insufficient bacteria but there may be other factors, e.g. if plants are dying, remove dead organic material. If new fish have been recently added then be aware that overstocking can overload the biofilter. In some cases ammonia may be present in tapwater. It is also possible for the beneficial nitrifying bacteria in the biofilter to die, either through chlorination or competition with heterotrophic bacteria and certain types of mould or algae.

 

[TwoTankAmin]

Glad to see somebody interested enough to respond.

1. Good answer. NH3 can pass through the gills into the blood stream, NH4+ can not. Basically the NH3 molecule is small enough to pass through fish gills and into the blood stream, NH4+ is larger and can not pass.

2.5.3 Accumulation in aquatic organisms

Accumulation of ammonia in the body can be due to either the inability to excrete or convert nitrogenous wastes or a net influx of NH[sub]3[/sub] from the environment. Externally, the concentration of NH[sub]3[/sub] , rather than NH[sub]4[/sub][sup]+[/sup] , is of concern, as biological membranes are permeable to NH[sub]3[/sub] but much less so to NH[sub]4[/sub][sup]+[/sup]. Consequently, NH[sub]3[/sub] , but not NH[sub]4[/sub][sup]+[/sup] , diffuses readily across the external surface into the body. As a result, if NH[sub]3[/sub] levels are high in the environment, ammonia levels in exposed animals increase as well.

From http/www.hc-sc.gc....nia_2_3-eng.php

2. Good answer again.

To avoid over burdening folks with more links and quotes it boils down to this. I have read a number of studies of fish and the toxic effects of NH3 and No2. In virtually every study the concetration of NH3 which is lethal to fish (LC[sub]50[/sub]) in ppm is always lower than that of nitrite. However, I will link to the cardinal tetra research. Scroll down to chart Table 2 B, You will see that at a .85 ppm concentration of NH3 (TAN of 35.6 ppm) killed 85% of the fish. However, a nitrite concentration of 1.5 ppm (1.75 times higer than .85) only killed 65%.
See http/www.scielo.br...n4/v38n4a23.pdf

3. Sorry, not so good an answer.

Firstly, in the same cardinal tetra study above a total ammonia concentration .9 ppm killed no fish. But lets get down to the real nitty gritty. Since we know it is NH3 that is toxic and that NH4+ is much less so, we should be concerned with the level of the former much more so than the latter. This is especially true when the time periods for exposure are limiteded, that is not beyond some number of days/weeks. So when we test for ammonia, it is important to know what the test kit measures. The majority of aquarium test kits measure total ammonia in the ion form. However, most research on the lethal/toxic effects of ammonia measure in terms of only nitrogen ions. What this means is we need to convert the total ammonia ion reading into a total ammonia nitrogen reading. To do this one must multiply the ion reading by .8 to convert it to the nitrogen value. If you are using the API ammonia test kit (the one most often recommended on this site) you need to adjust your test result accordingly. Thus a reading of .25 ppm it is actually more like .20 ppm (based on the article linked to in the first post).

But lets ignore this part of things for the moment and just look at .25 ppm of total ammonia and figure out how much of it is NH3. To do this requires knowing one's tank pH and temperature and then using a conversion chart or factoring chart to calculate the amount of NH3 present. The former is pretty simple and can be found here http/dataguru.org/...AmmoniaTox.html As you can see in almost every situation, NH3 will not be a problem, especially shorter term. What does this mean regarding a fish in cycle? There is little need to do anything unless your tank parameters put you into the small red areas on the chart. By lowering the total ammonia level when its at .25 ppm you are also extending the cycling time. So while you may be lowering the ammonia level you will also be exposing fish to a lower level for a more extended period. Now factor in that the ammonia nitrogen reading is .2 not .25 ppm and those red areas will almost vanish off the chart.

But there are even more factors to consider. The first is which dechlorinator one is using and when one is testing for ammonia. If one is using the most common kits, they will also contain an ammonia detoxifier. This is typical of SeaChem''s Prime for example. And here is what SeaChem says regarding ammonia testing is such cases:

Under the conditions of a salicylate kit the ammonia-Prime complex will be broken down eventually giving a false reading of ammonia (same as with other products like Prime&reg, so the key with a salicylate kit is to take the reading right away.

From http/www.seachem.c...FAQs/Prime.html
So what this means is unless that .25 ppm reading was obtained soon after adding the dechlor, the odds are you are getting a false reading. The .25 ppm is testing error and not ammonia being present.

Further, if one has followed the common directions for doing a fish in cycle one of the very first things it states is to choose a few hardy fish for cycling. Few is the key word there. The reason is different fish have more or less tolerance for ammonia. The term hardy basically refers to fish who are in gernerally less sensitive to ammonia and nitrite. The reason few is stressed is because it means there is a limit to how much ammonia will be produced before the AOB swing into high gear.

Finally, newly introduced fish are normally somewhat stressed to begin with. It takes them time to adapt to their new surroundings as well as to recover from the process of netting, bagging and being introduced to new conditions. So things like water changes are likely to stress them even more. Once fish have been in a new tank for some time (weeks to months), working in the tank becomes less stressfull. To support this the best i can offer is a personal observation. The longer my fish have been in their tanks, the less freaked out they are by water changes and vacuuming. fish that hid will now come out and peck at the siphon trying to eat the gits being sucked up inside. Often I have to shoo fish out of the way to do work. I would bet that most experienced fish keepers would report similarly. So where is the advantage in adding to stress to deal with a perceived problem that most likely is not really a danger?

And before people get up in arms about all this remember that during a fish in cycle the amount of time fish are exposed to ammonia overall should be fairly brief. Ammonia should peak in about 12-14 days and zero out within a week without doing any water changes. The peak should be somewhere in the 10 ppm range. Now it is one thing to want to reduce 10 ppm ot total ammonia to protect the fish and a totally different issue at .25 ppm. If one reads ,25 ppm on the way up, it is way too soon to do anything. If one reads .25 ppm on the way down, then there is almost never a need to do anything.

One last observation. When cycling with fish there is no reason not to seed the tank with bacteria by taking media, gravel or decor from a cycled tank. Just as this accelerates things in a fishless cycle, it will also do so for a fish in cycle. And of course one can also add one of the effective bacterial starter products. My experiences with DrTim's One and Only have all worked as "advertised" when ever I have used it as long as the tank pH wasnot under 6.5. It works best at higher pH levels- with 7.5 - 8.2 being optimmal.So even when cycling with fish there are ways one can minimize ammonia levels.

Almost the only time an accurate reading of .25 ppm for total ammonia ions is a worry is when it is in an established tank where ammonia should always read 0 using common test kits.

All that said, it is still preferable to cycle without fish if you can. Mistakes then can only kill bacteria and/or extend the cycling time.

 

[daizeUK]

Under the conditions of a salicylate kit the ammonia-Prime complex will be broken down eventually giving a false reading of ammonia (same as with other products like Prime&reg, so the key with a salicylate kit is to take the reading right away.

I'd like to go into this in more detail. What do they mean by a 'false reading of ammonia'? Do they mean that the ammonia-Prime complex breaks down to non-toxic ammonium? But if so, surely this is dependent on your temp and pH since that ammonium can freely exchange into toxic ammonia under the right conditions (e.g. in my tank I have a pH of around 8.1, so I have to be more wary of low ammonia readings )

I will also mention that the presence of chloramine in tap-water will give an ammonia reading regardless of whether the brand of dechlorinator contains ammonia-binding reagents, since the dechlorinating process will convert chloramine into ammonia at a ratio of 3:1. With ammonia-binding products the reading is simply delayed.

 

[TwoTankAmin]

Here is what I have learned regarding your questions. What SeaChem is saying is when one doses Prime and its ammonia binding properties come into effect, the ammonia is rendered not toxic. They mention something about imidium salt- which is extremely hard to research. However, since we know Prime does detox ammonia, I won't argue with their explanation, but would love to see more of the science and perhaps the "true" name for imidium salts. Googling it either using Web or Scholar is not very helpful with this. What they then say is once the ammonia is detoxified, it can still be used by the bacteria for somewhere around 48 hours. During this period a salicylate ammonia test kit will still show that detoxified substance as ammonia, which they consider to be a false reading. If one's bio-filter is not sufficiently developed to use up the detoxified ammonia then it will revert back to being the good old NH3 and Nh4+ we all know and love.

While you are correct about the fact that chloraminated water will also contain some level of ammonia, I am not so sure your conversion factor of a 3:1 ratio is accurate based on what I have read, The ideal ratio for creating monochloramine is 6:1 (chlorine:ammonia) although when it is being created they may use a 3-5:1 ratio. There is an interesting read on all of this here from a company in the Netherlands. http/www.lenntech....chloramines.htm If you have better info please add it to the discussion.

(Edited to correct spelling and grammar after my Backup-UPS decided to freak out and I had to pull it plug and restart it.)

 

[daizeUK]

What they then say is once the ammonia is detoxified, it can still be used by the bacteria for somewhere around 48 hours. During this period a salicylate ammonia test kit will still show that detoxified substance as ammonia, which they consider to be a false reading.

That makes perfect sense, although I was confused by the original statement "the ammonia-Prime complex will be broken down eventually giving a false reading of ammonia", the emphasis on eventually giving the impression that the temporarily detoxified ammonia complex will not be detected on ammonia tests.

While you are correct about the fact that chloraminated water will also contain some level of ammonia, I am not so sure your conversion factor of a 3:1 ratio is accurate based on what I have read, The ideal ratio for creating monochloramine is 6:1 (chlorine:ammonia) although when it is being created they may use a 3-5:1 ratio.

I think that is the ratio to create chloraminated water, however the type of chloramine is determined by this graph (from your lenntech link):

In our water supplies the pH will be in the range 6-8, which means monochloramines and dichloramines will be present, with the dichloramines more prevalent in acidic water supplies. That's presumably why they add the extra chlorine, to allow creation of dichloramines. However for me personally, with water straight out of the tap at pH 7.3, I can be fairly confident that I will have pure monochloramines. For those with more acidic tap water the conversion may not be so simple.

So, as long as we're just talking about monochloramine, I will quote from this discussion on practicalfishkeeping which made sense to me:

A chloramine molecule is NH2Cl, which means that it has 14 + 2 + 35 units of molecular weight - 68% is Chlorine, 32% is NH2 (ammonia sort of). This means that if you have 1mg/l chloramine, there is only about 0.33 (NH3) or 0.34 (NH4+) mg/l of ammonia.

I'd also like to delve into your ammonia toxicity chart in more depth. You seem to be placing a lot of trust in this chart to tell you when your ammonia levels are intolerable, so we need to be sure that those figures are really meaningful. Where are they deriving these numbers from?

For tests done on salmonids, half the salmonids tested died with exposure to .03ppm NH[sub]3[/sub]

Unfortunately their reference links don't seem to be working so I can't see the original research, but it seems these figures are based on research with salmon. I would guess that different species of fish have vastly different tolerances to ammonia and I'm not sure to what extent salmon are a good indicator for your average tropical freshwater aquarium. He semi-acknowledges this by stating "To my knowledge, we have no hard numbers for goldfish, but my fancy goldfish lived through around .03ppm for several weeks without adverse effects." Hmm... that sounds about as scientific to me as saying, "my fish are swimming around so they must be happy".

We know that his red numbers represent a concentration of ammonia at which half of a population of salmon died (0.03 ppm NH[sub]3[/sub]-N). Aside from the fact that I have no idea if my fish are more or less hardy than salmon, that sounds pretty bad and I wouldn't want my ammonia readings anywhere near there.

What do his orange numbers mean? I can't see any definition other than 'nearing danger zone'. Does that mean the orange numbers are the point at which deaths of salmon began to occur; i.e. anything under this is a guaranteed 'safe zone'? Or is it just some arbitrary figure that he picked at random... I don't know.

For my tank pH and temperature, an ammonia reading of 0.25ppm would indicate 0.017 mg/L NH[sub]3[/sub]-N. That's useful to know, but I can't tell from this chart if it's really safe.
What I would take from this chart is that I want to perform a water change before we reach those orange and red numbers, not wait until damage is starting to occur.

 

[TwoTankAmin]

In terms of chlorine and chloramine treatments for drinking water. there reallly are two levels to it. The first is what they may or may not do at the plant to make chloramines to disinfect. However, there are also government drinking water standards. What comes out of your tap is subject to these. For example in the States the federally mandated limit for chloramine in drinking water is 4 mg/L/ 4 ppm. We also have allowablbe limits for nitrate as well as many other things.

Those charts are based on the same formulas used for making the calculations. Would you like to see the same things at different sites? Here is a more abreviated from from the University of Florida. It is a factor, that is you use the number in the table to multiply your total ammonia reading to get the NH3 portion. http/edis.ifas.ufl.edu/LyraEDISServlet?command=getImageDetail&image_soid=FIGURE%203&document_soid=FA031&document_version=83976 It is not as extensive as the tables calculated on the other site. I have checked one against the other and I got the same results. But here is and interesting read from the Merck Verterinary manual.

NH[sub]3[/sub] is highly toxic and frequently limits fish production in intensive systems. It is also dynamic, and when it enters the aquatic system, an equilibrium is established between NH[sub]3[/sub] and ammonium (NH[sub]4[/sub] [sup]+[/sup]). Of the two, NH[sub]3[/sub] is far more toxic to fish, and its formation is favored by high pH and water temperature. When pH exceeds ~8.5, any NH[sub]3[/sub] present can be dangerous. In general, a normally functioning aquatic system should contain no measurable NH[sub]3[/sub] because as soon as it enters the system, it should be removed by bacteria ( Nitrosomonas spp ). Test kits used for aquaculture do not measure NH[sub]3[/sub] directly but instead measure the combination of NH[sub]3[/sub] and NH[sub]4[/sub], referred to as total ammonia nitrogen (TAN). A TAN of 1 mg/L is usually not cause for concern unless the pH is >8.5. However, if the amount of NH[sub]3[/sub] is increased, an explanation should be sought. The amount of toxic NH[sub]3[/sub] present can be calculated using the TAN, pH, and water temperature. When NH[sub]3[/sub] levels exceed 0.05 mg/L, damage to gills becomes apparent; levels of 2.0 mg/L are lethal for many fish.

(Blue color was added by me.)
From http/www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/170406.htm

The author of the tables to which I linked earlier is of the opinion that levels of NH3 of .03 ppm start to cause harm and .o2 ppm is approaching the danger level. These are his opinion based on his goldfish. but Merck states this at .05 ppm. Please not the author of the tables also lists the formula used to calculate the NH3 levels: NH[sub]3[/sub]=(Total Ammonia)/(1+10^[(0.0902-pH) + (2730/(273.2 + Temperature))] If you Google that formula you are going to find it used all over the place.

daize you really love to make me work

- I believe here s where that salmonid info is from http/www.water.ncsu.edu/watershedss/info/nh3.html

The Criterion Maximum Concentration (CMC), or acute criteria is based on short term exposure (one hour average). It is dependent on pH and fish species (salmonids or coldwater fish present, and the absence of salmonids) (EPA. 1999).

But I also have a number of bookmarked studies for specific fish and ammonia:

Acute toxicity and sublethal effects of ammonia and nitrite for juvenile cobia Rachycentron canadum at http/www.sciencedirect.com/science/article/pii/S0044848607004838

Acute and Postexposure Effects of Ammonia Toxicity on Juvenile Barramundi (Lates calcarifer [Bloch]) http/link.springer.com/article/10.1007%2Fs00244-006-0215-z

Acute and chronic toxicity of ammonia, nitrite, and nitrate to the endangered topeka shiner (Notropis topeka) and fathead minnows (Pimephales promelas) http/onlinelibrary.wiley.com/doi/10.1897/08-619.1/abstract;jsessionid=71A9B09E83596A07D9EB92E0819BB220.d02t01?userIsAuthenticated=false&deniedAccessCustomisedMessage=

Influence of pH, Salinity, Calcium, and Ammonia Source on Acute Ammonia Toxicity to Golden Shiners, Notemigonus crysoleucas http/onlinelibrary.wiley.com/doi/10.1111/j.1749-7345.2010.00382.x/abstract?userIsAuthenticated=false&deniedAccessCustomisedMessage=

Metabolic consequences of chronic sublethal ammonia exposure at cellular and subcellular levels in Nile tilapia brain http/www.sciencedirect.com/science/article/pii/S0044848609009363

AMMONIA MODELING FOR ASSESSING POTENTIAL TOXICITY TO FISH SPECIES IN THE RIO GRANDE, 1989–2002: http/www.esajournals.org/doi/abs/10.1890/06-1293.1?journalCode=ecap& http/www.esajournals.org/doi/abs/10.1890/06-1293.1?journalCode=ecap&

I would also note that the cardinal tetra link I provided has in it a few summaries as well:

The results obtained in this study are within the toxicity range suggested by Abdalla & MacNabb (1998), in which the lethal concentration of unionized ammonia for fish varies between 0.32 e 3.1 mg/L. Several authors have described the lethal levels (LC [sub]50[/sub]) of total and unionized ammonia for different fish species (Lemarié et al., 2004), such as Ictalurus puntactus, 45 mg/L NH3+ NH4+and 1.6 mg/L NH3 (Colt & Tchobanoglous, 1976), Oncorhynchus mykiss, 22 mg/L NH3+ NH4+ and 0.3-0.6 mg/L NH3 (Haywood, 1983), Odontesthes argentinensis, 0.76-0.96 mg/L NH3 (Ostrensky & Brugger,1992; Sampaio & Minillo, 2000), and Cichlasoma facetum, 2.95 mg/L NH3 (Piedras et al., 2006).

The reallly important things I am hoping folks will take away from this discussion is that, while ammonia in a cycled tank should effectively read 0 on most of the hobby test kits, when it doesn't, there is not necessarily a need to panic and act. That any level of total ammonia may or it may not be harming the fish depends on how much and for how long the fish are be exposed. Furthermore, not all fish are equally at risk for any given level. There is a lot more to it than having somebody categorically state that at .25 ppm as read on the API (or similar) test kit for total ammonia one must immediately do a water change or the fish will die. Especially when this is during a fishless cycle.

But lets say in an established tank you accidentally clean your bio-media with chlorinated water (not lethat levels) and as a result you kill some bacteria which results in an ammonia reading of .25 ppm. You moost likely do not to do anything at all since the killed off bacteria will be repalced quicly and the ammonia will not be there very long as a result.

Of course since we are discussing nitrogen, this would also encompass nitrite and nitrate levels too. But another part of this discussion involves the way we are measuring these things. Again we can use the site popular API nitrite test kit which is reading Nitrite ions not nitrite-n. At the upper limit of that test kit the -n reading would be 1.5 ppm. So now if during your fishless cycle you want to heed Dr. Hovanec's advice not to allow the nitrite-n levels to exceed 5 ppm, how does the average hobbyist know what this all means? That API kit stops at the equivalent of 1.5 ppm (5/3.3 = 1.51). Conversly to read 5 ppm nitrite-n that kit would have to go up to about 16 or 17 ppm,not the 5 ppm it does. So how many members have gotten a reading at the top of the API kit scale and rushed to do a water change? There may be only 1.6 ppm nitrogen-n or there could be 20 ppm, the kit doesn't know the difference.

 

[daizeUK]

I think a problem may be that I'm forgetting that the original question was discussing ammonia levels of 0.25ppm during a fish-in cycle. I'm doing a fishless cycle myself so I tend to think more in terms of ammonia levels in an established tank. Going back to your previous post I think there are two important points:

1) Fish-in cycling should be performed with only a few, ammonia-hardy fish

Unfortunately I think it is all too common that new tanks are cycled with whatever fish the purchaser happened to like in the LFS at the time. Sometimes the first time they will learn about cycling is by asking the forum, 'my fish don't look well and ammonia is reading 1 ppm, what do I do?' So I think it's safer to assume for the purpose of discussion that the fish weren't especially chosen for their tolerance of new tank syndrome.

Furthermore, there's a moral issue here even if the fish were chosen especially for hardiness. Is it acceptable to expose 'sacrificial' fish to higher ammonia concentrations than you would deem acceptable in an established tank? Personally I don't like the idea but, sentiment aside, I think it's important to be aware of the effects that different levels of ammonia will have so that we know how much the fish are suffering and what the long-term health effects will be.

2) By lowering the total ammonia level when its at .25 ppm you are also extending the cycling time. So while you may be lowering the ammonia level you will also be exposing fish to a lower level for a more extended period.

This is a very valid consideration for fish-in cycling and I think it would be helpful to better understand what the short and long term effects are and how we can best determine the point at which one outweighs the other.

One thing I will be especially wary of is research which only gives results in the form of 'X% of fish died at ammonia concentrations of Y mg/L over Z hours'. Unless we are strictly talking in terms of sacrifical fish, our goal isn't to ensure that 'only' half our fish die (!!!) but rather:

• Our fish do not suffer any short term pain or undue stress - as pet owners we want our fish to be healthy and happy, not just alive
• Our fish do not suffer any long term damage which will cause health problems or reduced life expectancy later.

Consequently I am expecting that we generally wish to control ammonia levels way below the point at which any fish are in danger of immediate death. That's why I think it's important when we see a chart labelled 'danger' and 'safe' to establish exactly what the author's definitions of these terms are. If his idea of safe is no deaths, then that's not good enough.

In pursuit of this I'm going to spend some time looking through all the information you've given to try to get a better idea of how much short-term suffering and long-term damage fish will endure at different concentrations of ammonia over given timeframes.

E.g. I've started with this example from the salmon research article (http/www.water.ncs...s/info/nh3.html)

Slightly elevated ammonia levels falling within the acceptable range may adversely impact aquatic life. Fish may experience a reduction in hatching success; reduction in growth rate and morphological development; and injury to gill tissue, liver, and kidneys (USEPA, 1987). Experiments have shown that exposure to un-ionized ammonia concentrations as low as 0.002 mg/l for six weeks causes hyperplasia of gill lining in salmon fingerlings and may lead to bacterial gill disease

Time for a little maths to translate 0.002 mg/L of NH[sub]3[/sub]-N into something we'd recognise from our ammonia test kit.
By rearranging your formula, total ammonia = NH[sub]3[/sub]-N * (1+10^ [(0.0902-pH) + (2730/(273.2 + temperature))])
For 0.002 mg/L of NH[sub]3[/sub]-N at 24.5°C that's 0.002 * (1+10^[9.2605-pH])
Total ammonia at pH 7 = 0.37 ppm
Total ammonia at pH 8 = 0.038 ppm
Phew! that's quite an equation, I hope I got that right?

Wait a minute... is this saying that at my tank pH of 8.1, a total ammonia reading of 0.038 ppm total ammonia for six weeks can cause long term damage to my fishes' gills? That's impossible to detect, I must have done something wrong in my calculations, surely?


I apologise for this poorly researched post, it will take me a bit of time to look through the links you've given and I get yelled at if I spend too much time on the computer

By the way - thanks for the info on the nitrites, I had thought that it was a bad thing to exceed 5ppm nitrite ion, so instead it's 16.5ppm nitrite ion. But as you say, the test kit doesn't go that high, either way.

 

[TwoTankAmin]

No - those charts are telling you that .038 ppm of NH3 is harmful, what level of total ammonia (both NH3 + NH4+) contain that .038 ppm of NH3 will depend on yhe pH and temp of the water. That formulas is supposed to tell you how much is NH3 based on a given total ammonia reading. You are working the formula the wrong way, so to speak. Normally one gets the reading for total ammonia and then tests for pH and measures the temp and then determines how much of that total is NH3. Of course one can work backwards, but what is the need for that. I agree with the concept of not wanting to cause harm or damage to the fish. As you note researchers do not have to share this concern in seeking answers. Basically, they tend to be looking at two different things. One is an attempt to determine lethal levels for things. That is at what point are things bad enough that at least half the subjects die- that LC[sub]50[/sub] number. And they want to know in what amount of time. In addition, as the cardinal tetra Table 2 B shows, they also want to know at what points fish begin to die and how that scales up. One of the more interesting things in that study was the fact that .9 ppm of total ammonia killed no fish during the 4 days (96h) time period.So that sure plays havoc with that .25 ppm thing from that point of view.The next thing the scientist may want to know is what the effects are from low level concentrations- more like those one might have during fish in cycling. For example the tilapia study exposed the fish to 5 ppm and 10 ppm for 70 days and then they basically dissected them to determine the physiological effects. But the baramundi study abstract concludes with this line:

A 3-week postexposure experiment on surviving individuals from the acute toxicity test, in clean water, indicated that exposure to acute concentrations up to 1.16 mg nonionized ammonia N L[sup]−1[/sup] did not have any significant effects on growth.

I wish I could see the entire study, but this indicates to me that in terms of growth, the ammonia concentrations that killed 1/2 the test subjects had little to no impact on the survivors give 3 weeks in clean water. Now other damage may have been done, we can't tell. But at least we can see that what killed half did not prevent the other half from growing up normally.There is a wealth of information out there. Go to Google Scholar and enter "ammonia toxicity in fish". Limit the time frame to 2000 and 2013 and you get back over 17,000 results. You can change the word ammonia to nitrite and you get back over 15,000. Even if only 10% of these results are relevant in some way to aquariums, that is still a wealth of information.My personal experience, though not science, in this matter would be last years acquisition of newly imported altum angels. They went into an uncycled tank at a pH of 4.2. After the first week I tested for ammonia in addition to pH and TDS. I began to get a .25 ppm reading on my API kit. But because of the pH I did nothing. This eventually climbed to .50 for which I again did nothing. I was doing regular water changes twice a week for other reason but not in response to the ammonia readings. I still have 15/22 fish some five months later. They look great and have grown just fine. All of the losses were the smallest of the fish and as far as I am concerned not the result of ammonia or nitrite (I never even tested for that) Moreover, the deaths occurred over several weeks and involved one fish at a time. But the most interesting thing is the tank somehow cycled itself. Today the tank is run at a pH between 6 and 6.5 and it has no ammonia.Considering how difficult wild Altums are to keep alive at all the first month or so, 15/22 for me was great. In 2011 a number of members on the wild angel site all purchased our Altums from the same source and of some 50-60 fish in four different people's tanks, 2 or 3 lived past 3 weeks. Mine actually went into a cycled tank at a pH just about 6.5. So I know ammonia did not get mine.The one thing I have come to believe is that the science part of ammonia toxicity and the unscientific emotional appeal of not wanting to harm the fish are not on the same page.Especially in light of all the issues surrounding the different scales used to measure the nitrogen complex at each stage, And then there is the issue of what any test may be measuring and what scale it is using. I also know that while NH4+ is not harmful in the same way as NH3, high levels of exposure or extended periods of low level exposure can both cause harm by burning. It is for this reason that total ammonia is important to know. We could simply use the NH3 tests from SeaChem etc. to read NH3 directly, but with fish in the tank that is not sufficient information to assure a no harm level overall. We should also know if there is a lot of NH4+ present.It seems to me, in regards to nitrogen, whether relative to cycling or just in relation to keeping a tank, pond or even an aqua culturing operation healthy and well managed, several things are important:1. Know how things are measured- i.e. there are different scales and which ones are being reference by tests or via recommendations makes a big difference.2. Know what is being measured by any test kit or meter and how accurate that test is. False readings are no more useful than inaccurate ones.3. Know how harmful any level of a nitrogen compound potentially is whether it is ammonia, nitrite or nitrate.4. Know how sensitive one's specific fish may be is also a big help if this information is available from a reliable source- i.e science not anecdotal presumption.5. Know how all of this relates to the bacteria in our tanks. There are significant difference between how nitrogen compounds affect bacteria vs fish.

 

[daizeUK]

Rather than searching for general ammonia toxicity, I have been concentrating on sub-lethal and long-term effects of ammonia poisoning.
 
I came across this study of sub-lethal ammonia concentration effects on Tilapia: http/ag.arizona.edu/azaqua/ista/ISTA8/mohamedshreif12.pdf
 
 
1.  Concentrations of NH3-N up to 0.05mg/l did not significantly affect the growth of tilapia fingerlings.  Concentrations of 0.1mg/l had an effect after two weeks of exposure.
2.  Anaemia becomes evident after 60 days exposure to 0.05mg/l NH3-N.
3.  Mild gill hyperplasia was evident after 75 days exposure at 0.01mg/l, increasing with severity at higher concentrations.  It is also noted that:
 

Kirk and Lewis (1993) reported that the gills of rainbow trout exposed to0.1 mg/l ammonia for 2 h exhibited deformation of the lamellae.

 
4.  Exposure for 75 days at the lowest concentration of 0.01mg/L showed evidence of some kidney and liver damage
 
The study concludes that tilapia are best kept at unionised ammonia concentrations of 0.01mg/l or less.  This translates to an API kit reading of 0.25ppm for around pH 7.8, or 0.5ppm at pH 7.5.
However for higher pH conditions it indicates that a test reading of 0.25ppm would be detrimental over long periods.
 
Unfortunately it's impossible to determine from this study what length of exposure is 'safe' before signs of damage begin to occur.  In terms of fish-in cycling this would be nice to know since exposure should be much shorter than 75 days in a filtered tank, but that information isn't available.
 
I would continue to conclude from this that in high pH tanks such as mine, any detectable amount of ammonia is detrimental to fish since damage may begin to occur at some indeterminable point at anywhere up to about two months but more probably sooner.
 
Based on this I would suggest to qualify your recommendation that a reading of 0.25ppm ammonia requires no action, to tanks of pH of under 7.8.  What do you think?

 

[TwoTankAmin]

I said that during fish in cycling a reading of .25 ppm Total ammonia is not usually an issue. If one is doing things right ammonia disappears in 10-14 days. I would never argue that longer term exposure is not a hazard. Even when there is no NH3, only NH4+, this will cause damage over the longer term by burning. But there is a big difference between exposure for the short term and long term.
 
And you also did no account for the nature of the API kit. Remember a reading of .25 is an ion reading and that translates into an ammonia-n reading of .20 ppm.
 
I also said: "But lets say in an established tank you accidentally clean your bio-media with chlorinated water (not lethal levels) and as a result you kill some bacteria which results in an ammonia reading of .25 ppm. You most likely do not to do anything at all since the killed off bacteria will be replaced quickly and the ammonia will not be there very long as a result."
 
Finally, that study you quoted involved baby fish aka fingerlings. I do not think most folks would use fry to cycle a tank. Moreover, I think you have misread it. For the most part the effects of .01 mg/l and .004 mg/l (the control) are almost identical. And the authors state this a number of times. Furthermore, there is no followup study regarding any recovery from the damage after the fish were returned to water without ammonia. So one can not conclude there was irreversible damage at any or all levels of exposure. That study also indicates that the NH3 level at which bad things are happening after 75 days is .05 mg/L the same level given in the Merck Veterinary Manual as the threshold level (and that is higher than the .03 ppm level suggested in the charts to which I link folks).
 
Oh yes, if you read the cardinal tetra study you will run across the following:
 

The exposure of freshwater or seawater fish to sublethal levels of ammonia can increase their subsequent resistance to lethal concentrations (EIFAC, 1973).

 
I will stand by everything I wrote above regarding .25 ppm ammonia as registered on a salicylate ammonia test kit that gives results in total ions in a tank being dechlorinated with products that detoxify ammonia.

 

[daizeUK]

And you also did no account for the nature of the API kit. Remember a reading of .25 is an ion reading and that translates into an ammonia-n reading of .20 ppm.

 
I thought I did?  I said that "The study concludes that tilapia are best kept at unionised ammonia concentrations of 0.01mg/l or less.  This translates to an API kit reading of 0.25ppm for around pH 7.8, or 0.5ppm at pH 7.5".  I got these figures by looking up on your chart http/dataguru.org/misc/aquarium/AmmoniaTox.html
 
 

Moreover, I think you have misread it. For the most part the effects of .01 mg/l and .004 mg/l (the control) are almost identical. And the authors state this a number of times.

 
I said that "Mild gill hyperplasia was evident after 75 days exposure at 0.01mg/l".  This is not identical to the control.  Also I said that the conclusion of the study was that the fingerlings should be kept at 0.01mg/l or less, thereby indicating that 0.01mg/l was deemed satisfactory even with the effects of gill hyperplasia, kidney and liver damage after long exposure.  My point is that the trial indicates that 0.01mg/l cannot be safely exceeded and I based my suggestion on this.
 
Yes they are only fingerlings but at least they are a common aquarium fish.  Much of the other research I have seen has been based off trout, salmon, sea bass and suchlike.
 
 

 Furthermore, there is no followup study regarding any recovery from the damage after the fish were returned to water without ammonia. So one can not conclude there was irreversible damage at any or all levels of exposure.

 
I think this is utterly irrelevant.  As responsible fishkeepers we should be aiming to protect the living animals in our care from pain and actual physical damage, whether seen or unseen.  Nobody would administer painful poison to a dog because "it's okay, he will recover later."   I think your approach to this is too clinical, the science is important but ultimately these are pets not lab rats.
 
 

The exposure of freshwater or seawater fish to sublethal levels of ammonia can increase their subsequent resistance to lethal concentrations (EIFAC, 1973).

 
Yes, I've seen this.  The key phrase is "resistance to lethal concentrations".  I refer you to this study on tilapia: http/www.tandfonline.com/doi/abs/10.1577/1548-8659(1979)108%3C383%3AATABTA%3E2.0.CO%3B2  which states that acclimation does not prevent gill damage, it only increases chances of survival:
Histopathological changes occurred in the gills of fish given both nonlethal and acute doses of ammonia. Capillary congestion, hemorrhaging, and telangiectasis were common symptoms of gill abnormalities.
 
My point is that the fish will still suffer even if they survive.  This should not be used as a reason to justify ammonia exposure.
 
 

I will stand by everything I wrote above regarding .25 ppm ammonia as registered on a salicylate ammonia test kit that gives results in total ions in a tank being dechlorinated with products that detoxify ammonia.

 
I agree that it is important to understand the side effects of products that detoxify ammonia and their effects on salicylate ammonia tests, but this is just one factor during a fish-in cycle.  My guess is that most people don't really want to understand the deep science behind it all; after all, how many people do you see participating in this thread?!  I think what most people will take away from this is that they never need to worry about a 0.25ppm ammonia reading, which I think is misleading and not in the fishes' best interests.
 
On the current evidence, my belief is that people with a high pH (7.8+) who care about the quality of life of their fish should not let their total ammonia exceed 0.25ppm and in these cases, after factors such as dechlorination are considered, a water change should be the recommended course of action.

 

[TwoTankAmin]

I thought I did?  I said that "The study concludes that tilapia are best kept at unionised ammonia concentrations of 0.01mg/l or less.  This translates to an API kit reading of 0.25ppm for around pH 7.8, or 0.5ppm at pH 7.5"

 
I do not believe you did. If your API test kit reads .25 that is ppm of Total ammonia ions. However those studies do not measure ammonia on that scale- they read ammonia-n. We have touched on this before. What it means is one needs to convert the API reading into its lower ammonia-n equivalent. So when the kit says .25 the ammonia-n is .20. Using a plain old ratio or .2/.25=.8, so your .01 of NH3 is really .008. or you could just change the .25 ppm to .3125 ppm.
 
Secondly, you are still ignoring the time factor. You equate keeping tilapia fingerlings for 75 days in ammonia to keeping larger fish in it for a week or two, comparing apples to oranges basically.  Keeping tilapia in under .01 ppm NH3 means long term not a week or two. Moreover you seem to have missed the information in the lines you quoted regarding the Tilapia aurea study it said the damage occured in fish exposed to both a non-lethal and then an acute dose. .25 ppm of total ammonia ions does not translate into an acute dose. So you have compared apples to oranges again. Finally, how many people keep trout?
 
One of the key take-aways from doing this sort of exploration of the literature should be the fact that different fish at different stages in their lives exhibit different reactions to the same level of ammonia exposure. Using a cherry picking approach and then attempting to generalize that to all fish is risky. I could single out the toadfish to prove to you that fish can survive levels of ammonia that would even kill a human being:
 

What makes the toadfish unique is that it can survive in ammonia concentrations that would kill almost every other creature, including man.
 
"The remarkable thing about these fish is that they can tolerate between 10 and 20 times more ammonia than our bodies—they are the champions of ammonia tolerance," said Patrick Walsh, a marine biologist at the University of Miami in Coral Gables, Florida, who has been studying toadfish for years.

From http/news.nationalgeographic.com/news/2002/09/0903_020903_TVtoadfish.html
 
Or I could use research on the weather loach (Misgurnus anguillicaudatus):
 

The level of ammonia reached in the plasma was the highest reported among fishes. Ammonia was not detoxified to urea, and urea excretion rate was unaffected by ammonia exposure. Fish acidified the water to reduce ammonia loading. Ammonia loading, unlike aerial exposure, did not induce glutamine synthesis, and there was no accumulation of glutamine. This is a unique observation different from those reported for other fishes in the literature.

From http/jeb.biologists.org/content/205/5/651.full
 
And then lets revisit the Merck Veterinary Manual. Why do you suppose it suggests:
 

The amount of toxic NH3 present can be calculated using the TAN, pH, and water temperature. When NH3 levels exceed 0.05 mg/L, damage to gills becomes apparent; levels of 2.0 mg/L are lethal for many fish.

(TAN is total ammonia nitrogen not to be confused with the total ammonia ions being measured by the API kit.)
 
It also says:
 

When pH exceeds ~8.5, any NH3 present can be dangerous.

Both from http/www.merckmanuals.com/vet/exotic_and_laboratory_animals/fish/environmental_diseases_of_fish.html
 
But how many folks keep tanks at 8.5 or above and cycle them with fish as opposed to fishlessly?. Plus the sentence says "can be", not "always is." So again I will stick by my statement that a reading of .25 ppm on a salicylate test kit reading total ions is almost never a cause for doing anything. I would go even further and say the potential stress of doing water changes on new fish combined with a longer exposure to somewhat lower ammonia levels is likely to be more harmful to most juvenile or adult tropical fish than leaving things alone for a number of days after which the ammonia level drops to 0.
 
It gets even more interesting when you read studies like this one which stated:
 

The finding that low levels of exogenous ammonia can serve as a growth stimulant without altering food consumption may be important for aquacultural practice, and challenges traditional dogma that the effects of ammonia are detrimental to growth.

From http/jeb.biologists.org/content/207/12/2043.long
 
or
 

This study aimed to elucidate the physiological effects of high environmental ammonia (HEA) following periods of feeding (2% body weight) and starvation (unfed for 7 days prior to sampling) in gold fish (Carassius auratus). Both groups of fish were exposed to HEA (1 mg/L; Flemish water quality guideline) for 0 h (control), 3 h, 12 h, 1 day, 4 days, 10 days, 21 days and 28 days.....................
 
Therefore, it was evident from our study that feeding ameliorates ammonia handling and reduces its toxicity during both routine and exhaustive swimming. Moreover, recovery was observed for some physiological parameters (e.g. MO2, ammonia excretion, Ucrit, plasma ammonia) during the last exposure periods (21–28 days) while for others (e.g. growth, tissue glycogen and protein content, muscle ammonia) effects only became apparent at this time.

From http/www.sciencedirect.com/science/article/pii/S0166445X1100316X
 
As far as I am concerned much of the literature would indicate that for most fish in most settings and for shorter term exposure, the .25 ppm TA level does not cause any permanent harm or damage.
 
But lets consider for a moment the current state of fish keeping. In almost any part of the world where there is internet access any budding fish keeper should be able to stumble across the information regarding fishless cycling. And most of them should be able to find some source of ammonia they can use. So exactly why would anybody choose to cycle with fish? They know if they are not careful they might harm or kill fish. So it seems to me those folks are pretty much making a conscious choice to take that risk if they go with fish in cycling.
 
I would go so far to argue the the primary reason a fish in cycling or fishless cycling encounters problems is the result of over zealous behavior on the part of the fish keeper. And I would further argue this is more often than not being caused by incomplete and/or improper advice being followed. For example, using too many or the wrong type or age of fish in a fish in cycling. This is slow process which needs to be done with as few and as hardy fish as possible. Most folks do not hear this enough.
 
Dosing too much ammonia too often will usually slow a cycle not speed it up. Yet folks are dumping ammonia into tanks willy nilly and then posting their cycles are stalled or are taking way way longer than they should. And this is reinforced by those who categorically state the bacteria will die off rapidly if not fed any ammonia. The beginner often takes this to mean dose more often.
 
And in all of this discussion nobody seems to take into consideration the potential for false readings. Using the most popular test kits and dechlorinators almost guarantees one will get some bad data. Nor do they talk to older folks who have kept fish for decades and had to cycle their tanks before hobbyists began to adopt fishless cycling in numbers. Ask some of the old timers how they made out and you will hear many reports of tanks being cycled and fish not being lost which then lived long lives in those tanks. And I will bet dollars to donuts their ammonia levels went well above .25 ppm for days.
 
I would point out that the article in the Beginner Section on this site on cycling with fish says nothing about which fish or how many fish one should use at the outset of a fish in cycle. It makes no mention of how the API test kit measures even while saying it is very popular with folks here. It makes no mention of NH3 vs NH4+. If one really wants to know what harm ammonia may be doing, they should be told to use SeaChem's ammonia kit which can measure NH3 directly no matter what dechlor is in use.
 
So here is my next question. If you want to make the argument that one must blindly change water at .25 ppm on an API test kit when cycling with fish in, can you show me research which shows what ammonia levels for what exposure times cause irreversible harm to zebra danios or most barbs (for warm water) or goldfish (for cool water)? These are the most commonly suggested ones for fw fish in cycling (I believe damsels or mollies are suggested for sw tanks?).