Question About The Science Of Co2

[Adelphie]

Not a specific issue or question about my aquarium, more of a curiosity.

My ideal situation would to be able to simulate a natural highly planted pool which needs very little tinkering/external influence from me in order to work. Which leads me to my question:

In the natural environment where does the CO2 needed for plants to flourish come from? I understand the chemistry of CO2 fertilization on land crops (I wrote my dissertation on it and could bore you for hours!), but I don't know what the natural source for it in the high levels suggested for a healthy planted tank.

Any ideas?

 

[three-fingers]

For aquatic plants the natural source of CO2 would be decomposition of the substrate.
However, CO2 is always very limited underwater in nature, so a lot of plants make use of bicarbonates where CO2 is limited.
Loads of aquatic plants are really more amphibious and will also grow aerial leaves to cheat and gain access to atmospheric CO2 as well.

Simply put, in nature, plants simply just don't get the same levels of CO2 that they do in tanks with CO2 injection.

 

[SuperColey1]

And in nature you don't see the kind of health in plants that we get in well balanced planted 'algae free' tanks!!!

If you think of a pool it will likely only have plants near the edges of the water and not in the centre. Stagnant pools turn into algae ridden smelly green or brown pools.

AC

 

[Colin_T]

I have to disagree with you SuperColey. There are plenty of nice healthy plants in the wild and they look just as good as the stuff in tanks. And there are plenty of Asian aquatic plant farmers that would disagree with you as well. They don't use CO2 on their ponds and their plants look pretty good. And their ponds don't turn into smelly brown or green pools. In fact I have never seen a natural waterway (that is located away from the polluted cities) that is green or brown soup.
It's the excess nutrients from agricultural runoff that encourages algal problems in local waterways. If they aren't full of extra nutrients then the CO2 levels would be sufficient to keep the plants happy and the algae at bay.

 

[SuperColey1]

Firstly I said stagnant pools not waterways!!! Waterways have natural flow in them as do Asian 'ponds' via filtration.

Secondly it has long been proven that the original assumptions by water authorities saying that excess nutrients (they blamed phosphates) were not the cause of algae within local waterways.

If this were true then we would be going by the light versus CO2 versus nutrients aregument which sends us back at least 10 years.

For the amount of light supplied by nature means that with the limited CO2 available in natural waterways that plants would not be able to grow to the potential light available and we would see algal growth!!!

Algae is caused by ammonia not inorganic run off. It can feed off inorganic fertilisers but only once triggered by ammonia.

If you look at a river there will be plants in the shade towards the river bank but hardly anything in the centre. Even more the case in fast flowing rivers.

Look at a reasonable flow stream in your area and photograph the plants in the middle for me.

AC

 

[Colin_T]

A lot of the waterways in Australia are stagnant pools, certainly for half the year they are, and that’s assuming they don’t dry up completely.
Most Asian plant farms don’t have filters on their plant ponds.

All the government departments that I know of are still blaming nutrients for algal problems in metropolitan waterways. They have plenty of scientists and lots of money to study the problem. And if nutrients like nitrates & phosphates aren’t causing the algal blooms in the rivers, then what is?

If algae is triggered by ammonia then why don’t all fish tanks have algae problems? Every aquarium has fish producing ammonia and the filters pick it up and convert it to nitrite and nitrate. The average aquarium has a slight trace of ammonia being produced continuously by the tank inhabitants and this level goes up after feeding, (albeit only for a short time). On the other hand, if the filters are working really well and getting rid of all the ammonia straight away, why do some tanks get serious algae problems even when they have a 0 ammonia reading?

Plants generally don’t grow in the middle of rivers because the water is too deep and not enough light gets to the bottom. The same applies to corals in the ocean. Most corals only grow in the shallows because that is where the light is. As you get into deeper water any corals that remain are plankton feeders and do not photosynthesise. There just isn’t enough light getting down to them in the deeper water.

The only fast flowing creek around here is full of a Potomageton sp. It lives in low light and shallow fast flowing water and doesn’t do well in tanks.

 

[Truck]

If algae is triggered by ammonia then why don’t all fish tanks have algae problems? Every aquarium has fish producing ammonia and the filters pick it up and convert it to nitrite and nitrate. The average aquarium has a slight trace of ammonia being produced continuously by the tank inhabitants and this level goes up after feeding, (albeit only for a short time). On the other hand, if the filters are working really well and getting rid of all the ammonia straight away, why do some tanks get serious algae problems even when they have a 0 ammonia reading?
.

to much light, silicates being leaked from silicone

 

[Spiceweasel69]

.[/quote]
to much light, silicates being leaked from silicone
[/quote]


Really. Aqueous silicates - from silicone. I cant see how that would work.

Eutrophocation is generally caused by overfertilisation and does require an ammonia spike, but id have to agree with COlin that it is the excess nutrients causing the algae blooms.

 

[Truck]

excess nutrients dont cause algae booms, they feed them.

 

[raptorrex]

And in nature you don't see the kind of health in plants that we get in well balanced planted 'algae free' tanks!!!

If you think of a pool it will likely only have plants near the edges of the water and not in the centre. Stagnant pools turn into algae ridden smelly green or brown pools.

AC

depends on what you term "stagnant"! not everyone has the same idea of, exactly, what it is. though it only means one thing, too few understand its real definition.
its far, from being a stinking algae covered, death trap. lillys, frogs and a number of fish, including gars, bettas, the odd barb even some turtles, all prefer stagnant water. this paints a picture, more like the comments by Colin, I'm afraid.

 

[Dave Spencer]

If algae is triggered by ammonia then why don’t all fish tanks have algae problems?

Colin, visit the Barr Report some time instead of the seventies.

why do some tanks get serious algae problems even when they have a 0 ammonia reading?

Zero based on what, hobby test kits?

Plants generally don’t grow in the middle of rivers because the water is too deep and not enough light gets to the bottom. The same applies to corals in the ocean. Most corals only grow in the shallows because that is where the light is. As you get into deeper water any corals that remain are plankton feeders and do not photosynthesise. There just isn’t enough light getting down to them in the deeper water.

Lets not compare rivers to the depths of the oceans.

It has been proven, and I really am not going to dig the references up again (find them yourself), that show that algae was in bloom in those waterways before the nutrients got washed in off the fields etc. Add the same conditions to a water way where plants are prevalent you will get more plants. Was there no algae before mans agricultural activity.

I add 5ppm nitrates daily to maintain around 25ppm, and .5ppm phosphates daily to maintain 4ppm to all my tanks. Where is the algae?

Colin, I have asked you many times to put your tanks up on this forum to back your principles up, yet you never do. Read the EI sticky for crying out loud and stop trying to hold back the planted side of the hobby. You clearly know precious little about it.

Excess nutrients do not casue algae. I and thousands of others prove it on a daily basis when we dose our tanks.

When was the last time you was able to trigger algae deliberately, Colin? I can do it with CO2. And I can clear it. All in a tank with nitrates at 25ppm and phosphates at 4ppm.

I love it when people who know nothing about planted tanks come on here trying to spout out tired old rubbish about how it should be done. Let us see you back it up some time.

Dave.

 

[Adelphie]

Thanks for the replies... I didn't mean to start any rows!

@SuperColey: Although I think that with precision and care you could get a stagnant pool which is not algae ridden (or algae free) in reality I reckon it would be very, very hard so I am sticking to having a decent amount of flow in there.

@ Dave & Colin: It is my understanding that fertilizer run off from agricultural processes does not in itself cause algae blooms, however it promotes growing conditions for both plants and algae of which surface plants are usually the first to benefit. This results in less natural light getting to any of the plants below, and cause optimum conditions for the algae to bloom. This then causes the plants to start to die down and rot which in turn ends up damaging any aquatic life (or at least that is the way I learned it back in my agronomy classes).

In short overdosing fert in the aquarium does not lead to negative results as you control what goes into the tank, put in CO2 to promote plant growth and remove any surface plants which are blocking light, but in natural waterways there is nobody to oversee these processes.

 

[plantbrain]

I honestly believe Colin's heart is in the right place here.

However we often see and read reports about natural systems and think they are all the same, they are very specific systems.
And there are only a few things we can do to manage them, we cannot control light over a large lake practically or change the duration of light for it? Add CO2 at high levels?
Maintain same temp over a season?

What about the systems that actually have aquatic plants at a similar biomass ratio as own aquariums with plants?

That's a specific question and there is a well defined specific answer:
http/fishweb.ifas.ufl.edu/Faculty%20Pubs.../macrophyte.pdf

You can see from the research on sub and tropical lakes WHERE AQUATIC PLANTS ARE PRESENT, there's no relationship based on 319 lakes, quite few
N or P, no correlation.

If you add more nutrients to a weed choked lake, you get more aquatic weeds, no algae.
Wouldn't be great if all we had to do for aquatic weed problems was simple add some PO4 or NO3 to kill the weeds and have a nice green pea soup?
Doesn't work like that. Most folks do not consider 30-50% surface area coverage for submersed vegetation when you ask them about their studies and the northern lakes with ice etc, sorry, I do not have ice in my tank.
Aquatic plants when in high enough biomass define the system, not algae or nutrients.

If you want to look at algae and nutrients and aquatic plants, you need to find studies that apply to your question.
I went and worked at this same lab where the authors above published this paper. I kill aquatic weeds for my research. Man that would be great if the farmer just needed to dump runoff into the Sacramento and San Joquin rivers to kill the thousand of acres of infested water in the Delta here.

We have Egeria densa , Hyacinth, Cabomba, a dozen or so native pondweeds, P. crispus, Eurasian milfoil etc etc.........they spend about 8 million$ a year to kill the boating ways clear killing it.
Now CA have a huge valley and more year round ag production than most places, all this water goes into the delta, and yet we have no algae issues and horrid weed problems.
We cannot control the sun light, we cannot control the CO2, but we can control N and P coming in............so how do you think we should do that? We could use aquatic wetland plants as filters to remove the N and P and sequester it. The trimmings can be used for green manures for fields. But.......we have rice, so that water is sent there and then on top the the orchards and either is transpired or seeps into ground water for recharge.

As far as NH4, if you have enough plant biomass, relative to a loading rate of NH4, then the NH4 is rapidly sequestered, much like in our aquariums.
If you start dumping high rates of NH4 from say a sewer plant, then you will end up killing the plants with high NH4, which is fairly toxic to most things, all the decaying matter causes changes in the CO2 in the water and the O2, and induce algae.
The same is true if you add too many fish to a high light CO2 enriched system, you will get algae and plants will suffer. Adding a little bit of NH4 loading is not big deal, adding a lot is. CO2 variation is also a good signal for algae spores to germinate and that's what the key for control of algae is all about, preventing germination of algae spores. Light is also a germinating signal, add a lot and it will speed and increase the % germination. It's not all about nutrients, CO2 and light are also where it all starts, and algae are not CO2, plants most of the time in natural systems are.

Nor are such relationships always direct, often times limiting one thing causes a downstream affect on another, leading some to think that high PO4 causes algae, when actually the limitation of PO4 simply masked the CO2 issue. You did not test the system independently, you had a CO2 issue once you removed the PO4 limitation via dosing.

If you go back and check the CO2, and keep it independent, then adding PO4 liberally is now no longer an issue and you do not have algae.
This is why some thought and observed PO4 causing algae in some cases and why others with good CO2 did not and only had nice growth.
Taking the limitations from nutrients away causes a increase in CO2 demand.

Likewise, adding more light increases CO2 demand, which in turn increases nutrient demand. the reverse is also true, less light=> less CO2 demand= > less nutrient demand. This explains non CO2 planted tanks and why some tanks do fine with little or no added nutrients from KNO3 etc, and others need more, they generally have more light, less sediment ferts/fish waste etc.

This is basic horticulture/plant physiology, simple logic about how a plant acquires resources and is able to grow.
The academic research and test results we can do/have done test and see for ourselves also supports this view.

You can keep saying it ain't so, but in the face of test, research that is very specific to our case here, and simply the fact that many do it without the results you claim should give you a lot of reason to doubt the validity of the claim.
Either that or we are all in some massive conspiracy

The AGA winner in 2003 used EI dosing, non limiting nutrients.
So does this guy , this is an old pic, the tank looks really awesome now, I think we will put it in the ADA contest this coming year to see.

And to give a bit of an idea of the scale:

1/3 of the tank:

I installed a CO2 dissolved meter that's not influenced by pH/KH etc and we have run this for several months at 45ppm without any issues thus far to fish, which full large discus tend to be the most sensitive of species.
The dosing is fairly rich.

If you can explain why such tanks do not have algae even with high PO4/NO3/Fe etc, I'm all ears.
Because based on your hypothesis, it should be covered in algae. We tested it and it's clearly not the case. Therefore such hypoothesis must be rejected based on results, not just some thing you want to believe or not, and then look for other issues for algae presence. Like CO2, light etc.

This is not just all about nutrients like the nature systems that have been damaged by humans.
Well, we are doing somethings to CO2 these days as well..........but not like we ever do in the aquarium.

Perhaps this clears a few things up for folks.
Hopefully


Regards,
Tom Barr

 

[SuperColey1]

It is my understanding that fertilizer run off from agricultural processes does not in itself cause algae blooms, however it promotes growing conditions for both plants and algae of which surface plants are usually the first to benefit. This results in less natural light getting to any of the plants below, and cause optimum conditions for the algae to bloom. This then causes the plants to start to die down and rot which in turn ends up damaging any aquatic life

In short overdosing fert in the aquarium does not lead to negative results as you control what goes into the tank, put in CO2 to promote plant growth and remove any surface plants which are blocking light, but in natural waterways there is nobody to oversee these processes.

I have no evidence to back up this 'theory' but I think that the above is wrong on what is understood today.

The fertilser indeed will 'feed' algae just as it will 'feed' plants so this is correct. However Algae needs less 'food' and less CO2 than plants and therefore if there is not sufficient nutrient for the plants then algae will be the clear winner.

However if the theory of surface plants (floaters) being the first to benefit then they also have access to the CO2 in the air being at the surface and therefore become non CO2 limited and thus will draw much much more nutrient than anything below. Also because it blocks light to the plants below they will die but so will the algae which also needs light. This is why a low light tank is much easier to manage than a highlight tank. The nutrient and CO2 demand from the plants is much less than in a highlight situation.

So if a 'pool' or waterway had fert runoff and on your theory the surface plants are the first to benefit then they would overtake everything (including algae). the water underneath would then be more likely to be clear with almost no prescence of algae or plants because there would be no light for either. The surface plants with direct access to CO2 would then be using much much more nutrient to go with their increased growth thus removing most of the food for algae and plants alike.

As for the plants rotting down I disagree here. There would have to be massive sudden rotting of huge plantmass (and algae) due to the lack of light for this to happen and most surface plants are excessive feeders anyway which is why some people use Riccia and duckweed to suck up nutrient (following the old excess nutrient theories.) The truth is they are associating the less algae with the Riccia/duckweed removing excess nutrient. This is the wrong assumption as it is the lower light which is in effect the cause of this change.

As I say I have no backup on this theory but I would bet I was pretty much closer than disproven theories of old even funded in the millions!!! Reading of the barrreport can confirm this in much more scientific detail for anyone who is interested in learning that maybe what we are told is not always correct!!!

I remember all the financial experts, property analysts, politicians saying 3,4,5 years ago that the housing bubble would not burst, that there would be no recession, that a short stagnation would be the worst case scenario. My wife wanted to buy a house in 2006 before the prices went up further. I refused telling her that there would be a recession in 2008 and I would buy a house in 2010-2012 when prices would bottom out substantially.

I am no expert on that either but I was 1 year out on the recession (if you believe it didn't happen last year) and at the moment it looks like house prices will be ideal from 2010 to possibly 2015.

The argument is that what the experts say is not always right. This can go for Tom as well but then he tests things. He wants to prove to himself before he goes dismissing other theories.

As Dave says. I have high fishload. I have very high turnover. I dose far in excess of plants needs regarding NPK. I currently use high power high penetration LED lighting. You can see the result in my signature!!! This tank houses breeding black corys and they are getting a bit too carried away these days. So the high ferts, high CO2 is not exactly causing problems is it!!! Plus it is nice to look at.

AC

 

[plantbrain]

excess nutrients dont cause algae booms, they feed them.

True, and the same is true for aquatic weeds, add more nutrients, you get more weeds.

If you consider the life history of algae and aquatic plants, they are radically different, algae form spores, cells live relatively a short time, they germinate, just like annual plant seeds etc when conditions are ripe.
Aquatic plants generally for us, are perennial, cuttings and clones etc. They just need good stable CO2, light and nutrients.


Regards,
Tom Barr