Nitrate removal

Sorry in advance for the length of this!
I'm in the UK and my two water is 30ppm, but my tank runs at around 10ppm even though it is heavily stocked, so clearly my tank us dealing with all of the nitrate that the fish produce, and more. It is heavily planted and my filter deals with some of it through anaerobic activity.
Bear in mind that this means that when I do a water change I am ADDING nitrate, not diluting it. I do 2 changes a week which total about 15%. That is low by most standards, but I have done this for decades and it works. I did once decide to fall in line and tried upping this to 25% per week, but at that level I was adding too much nitrate, the tank couldn't handle it, and levels rose to 40ppm over a few months. At that level I found that plants stopped growing so well which compounded the issue and left me in a catch 22 - I needed to get plants growing again to tackle the nitrate, but I needed to get nitrate down first to make the plants grow! Water changes wouldn't help as they were what the caused the problem.
What I did was to use NitratEx resin to get it down to 15ppm. Plants then started growing again, though I had to use the resin a second time before the plants reached a sufficient rate of growth.
Although that seemed to work, I also refreshed my filter media and added some BioNitrateEx to make sure it was doing its job properly.
I have used this technique when setting up a new tank too as the same catch 22 applied.
Every tank is different as is everyone's source water, so I'm not intending to give specific advice here. However, I just wanted to point out that large scale water changes aren't always the answer, indeed, they can be the problem! Don't be afraid to use nitrate absorbing resin as a short term solution, they do have a place, and natural, nitrate reduction through biological filtration is a thing and should be encouraged. Unless you are running your filter really slowly, special media is a good idea. I used to run mine really slowly, but my current filter doesn't allow me to turn the flow down. It's beneficial to circulate your water well, but it doesn't all need to go through the filter. Your filter will work perfectly well at a turnover of once per hour if this is supplimented with a wave maker pump or similar. At that level of flow you will definitely get nitrate reduction in the filter. I did put a baffle in my faster filter to create an area of lower flow and this appeared to have an effect, however, it was a bit if a pain at cleaning time which is why I switched to special media instead.
I did once read that if nitrate falls below too low, toxins can develop. The article went into great detail, but unfortunately I can neither remember what issues might arise nor can I now find that article! I do remember that the advice was that a level of about 10ppm was probably ideal. Whether that is true I can't say, however, my tank seems to stabilise at that level because if it falls below that, my plants slow up, so on that basis alone, that level seems to be good!

Can you hook up a water filter from your mains? I think they are essentially activated carbon but perhaps might do the trick.

raylove said:

I'm in the UK and my two water is 30ppm, but my tank runs at around 10ppm even though it is heavily stocked, so clearly my tank us dealing with all of the nitrate that the fish produce, and more. It is heavily planted and my filter deals with some of it through anaerobic activity.

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Aquariums have too much oxygen for anaerobic bacteria to live, and power filters in aquariums have too much water flow for anaerobic bacteria to live in them. The bacteria living in your filter won't be doing anything to remove nitrate.

If you have a nitrate removing substance in the filter, or special media that encourages anaerobic pockets, then they can help remove nitrates. But normal filter media/ materials will not become anaerobic in an aquarium filter that is working properly.

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raylove said:

I do 2 changes a week which total about 15%. That is low by most standards, but I have done this for decades and it works. I did once decide to fall in line and tried upping this to 25% per week, but at that level I was adding too much nitrate, the tank couldn't handle it, and levels rose to 40ppm over a few months.

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Did you have the same type and number of plants in the tank as you do today, when you increased the water changes to 25%?

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raylove said:

I did once read that if nitrate falls below too low, toxins can develop. The article went into great detail, but unfortunately I can neither remember what issues might arise nor can I now find that article! I do remember that the advice was that a level of about 10ppm was probably ideal. Whether that is true I can't say, however, my tank seems to stabilise at that level because if it falls below that, my plants slow up, so on that basis alone, that level seems to be good!

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Most natural waterways never have ammonia, nitrite or nitrate and any level of these can harm or kill fish. The only reason waterways have any of these in now is due to people adding chemicals to the environment, which get into the water. The most common chemicals that cause this are fertilisers used for gardens, lawns and farming crops for human consumption.

Aquarium plants do like some nitrates and if you have a heavily planted tank, then a lot of people do add nitrates for the plants. But fish never evolved with ammonia, nitrite or nitrate and you should try to keep these levels as close to 0ppm as possible.

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If you have nitrates in the tap water, you can filter the water before using it, or put some tap water in a holding container and add some floating plants. Leave the plants in there until the nitrates are gone and then use that water for the fish tank.

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You do water changes for 2 main reasons.
1) to reduce nutrients like ammonia, nitrite & nitrate.
2) to dilute disease organisms in the water.

Fish live in a soup of microscopic organisms including bacteria, fungus, viruses, protozoans, worms, flukes and various other things that make your skin crawl. Doing a big water change and gravel cleaning the substrate on a regular basis will dilute these organisms and reduce their numbers in the water, thus making it a safer and healthier environment for the fish.

If you do a 25% water change each week you leave behind 75% of the bad stuff in the water.
If you do a 50% water change each week you leave behind 50% of the bad stuff in the water.
If you do a 75% water change each week you leave behind 25% of the bad stuff in the water.

Fish live in their own waste. Their tank and filter is full of fish poop. The water they breath is filtered through fish poop. Cleaning filters, gravel and doing big regular water changes, removes a lot of this poop and harmful micro-organisms, and makes the environment cleaner and healthier for the fish.

Colin_T said:

Aquariums have too much oxygen for anaerobic bacteria to live, and power filters in aquariums have too much water flow for anaerobic bacteria to live in them. The bacteria living in your filter won't be doing anything to remove nitrate.

If you have a nitrate removing substance in the filter, or special media that encourages anaerobic pockets, then they can help remove nitrates. But normal filter media/ materials will not become anaerobic in an aquarium filter that is working properly.

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Did you have the same type and number of plants in the tank as you do today, when you increased the water changes to 25%?

-------------------

Most natural waterways never have ammonia, nitrite or nitrate and any level of these can harm or kill fish. The only reason waterways have any of these in now is due to people adding chemicals to the environment, which get into the water. The most common chemicals that cause this are fertilisers used for gardens, lawns and farming crops for human consumption.

Aquarium plants do like some nitrates and if you have a heavily planted tank, then a lot of people do add nitrates for the plants. But fish never evolved with ammonia, nitrite or nitrate and you should try to keep these levels as close to 0ppm as possible.

-------------------
If you have nitrates in the tap water, you can filter the water before using it, or put some tap water in a holding container and add some floating plants. Leave the plants in there until the nitrates are gone and then use that water for the fish tank.

-------------------
You do water changes for 2 main reasons.
1) to reduce nutrients like ammonia, nitrite & nitrate.
2) to dilute disease organisms in the water.

Fish live in a soup of microscopic organisms including bacteria, fungus, viruses, protozoans, worms, flukes and various other things that make your skin crawl. Doing a big water change and gravel cleaning the substrate on a regular basis will dilute these organisms and reduce their numbers in the water, thus making it a safer and healthier environment for the fish.

If you do a 25% water change each week you leave behind 75% of the bad stuff in the water.
If you do a 50% water change each week you leave behind 50% of the bad stuff in the water.
If you do a 75% water change each week you leave behind 25% of the bad stuff in the water.

Fish live in their own waste. Their tank and filter is full of fish poop. The water they breath is filtered through fish poop. Cleaning filters, gravel and doing big regular water changes, removes a lot of this poop and harmful micro-organisms, and makes the environment cleaner and healthier for the fish.

Click to expand...

I disagree, anaerobic bacteria can live in a power filter if the flow is limited and you have enough of the correct media. Media such as Siporax is marketed on this basis. Provided the pores are fine enough there will be areas deep in the media where flow is limited, however, as I say, limiting the flow helps or you can add baffles. Having done all that though it is difficult to prove this is working in a planted tank! BioNitratex does however seem to work as it gives you visual clues. With a back up circulatary pump, you don't need to filter the water 4 times an hour. The filters I use these days don't allow me to turn them down, but in past when I have done so my tanks ran perfectly fine and the filters removed as much muck as they did at higher flow rates. Biological action was also never an issue.
Yes, I did have the same number of plants when I upped my water changes, but they started to suffer after a couple of months and that was when I discovered the increased nitrate and figured out what was going wrong. It also explained why I always found it difficult to establish plants in a new tank. Once I figured that out I started taking the steps described earlier, and I no longer have that problem.
Plants do need some nitrate so I don't feel the need to reduce what is in the tap water - if I did I feel I would probably have to use ferts which contain nitrate as my tank currently deals with everything the fish produce and more.
I wouldn't argue a case for keeping nitrates at 10ppm because I really can't remember what the reasoning was. It was a very technical article though, and the guy seemed to know what he was talking about! My water always settles at 5-10ppm and I'm happy with that.
I should say that although I only change 15% per week, I always do a thorough gravel cleaning at every water change, and I keep my filter in tip top shape too. I can only say that I have kept fish for 45 years since I was a boy, my fish spawn regularly, live to ripe old ages, I haven't had to treat for any diseases for maybe 20 years and my water is crystal clear with no yellowing. I appreciate that there are many other nasties besides nitrate, but after 45 years I think I can definitely say this regime is enough to deal with these - I would have found out by now if it wasn't!
The only time I have kept a non planted tank was years ago when I kept marines and I did have to make larger changes, but even then I think 25-30% was sufficient from memory.
Water changes are definitely essential but a well maintained, planted tank shouldn't need large scale changes in my view. Every tank is different of course so it's difficult to generalise, but hopefully my experience is food for thought!

I have a heavily overstocked 125 long with an Oscar, 3 pacu's, and a pleco all over 12" long plus 2 parrots and 5 silver dollars. We are setting up a 300 for these brutes as they grew much faster than we had anticipated (we bought them as 1" juveniles less than 2 years ago!). The bioload is very high such that I have 2 Fluval FX6's operating. The latter stoically keeps ammonia and nitrites at 0 but nitrates are very difficult to control. Typically the nitrates reach 80ppm in less than a week so we've been performing 2, 50% WC's/week to control it until the large tank is ready.

Then we tried adding riparian plants growing out of the top. The Oscars and Pacu's are VERY active and swim into and collide with virtually anything as well as they easily can jump out of the tank so rooted plants were impossible and covers are essential.

We replaced the typical tank covers with plastic lighting grids and added just 2, pothos plants in the tank above and created a 'forest' of Lucky Bamboo in a 75 as well. Admittedly it was really an aesthetic choice, and due to the Oscar and pacu's knocking everything over and uproot anything I try to plant! The bamboo forest is rooted and supported by the grid cover so it's not going anywhere. They bit at the stalks for 2 days and gave up.

But the nitrate reduction was so profound, I'm still in disbelief.

In the Oscar/Pacu tank (125), 1 typical week before a WC we saw nitrates somewhere between 80ppm and 160ppm. Now after 2 weeks with the plants in the image below, they've yet to reach 20ppm! In fact, they're still dropping over time. It's been 8 days, the longest I've ever allowed this tank to go without a WC and nitrates read between 10ppm and 20ppm.

In the 75 below, we used stalks of Lucky Bamboo. These fishes have a far lower bioload than the brutes in the 125 so this is not of value as a comparison but that tank with 10 EBA's and 2 Plecos has yet to exceed 5ppm on the nitrates since the bamboo and it was circa 40ppm before in the same time period.

"Brown Algae" has all but vanished. Water clarity improved not unlike when you first add a pack of Purigen or the like. I must admit I was so shocked by the nitrate reduction I bought a 2nd test kit in case one of the bottles was bad!

In any event, I wonder if any quantization of the effects of riparian plants in aquariums exists?

This is really interesting to me as I had noticed, despite high tap water nitrates, my tank water has been lower; 5 at the last reading. I have a reasonably well planted tank, although they are all new and not well established, but have plenty of Salvinia which grows like wildfire. So now I know that is where my nitrates are going. I knew plants used nitrates, but not to that extent.

I am changing water little and often too, since each time I risk adding nitrates rather than diluting them. It also avoids big pH changes since my buffering capacity is very low. There are times, I think, when small water changes are safer overall. If they minimise the stress for the fish they make it less likely that the disease soup in which they live will make them ill.

I completely agree with everything you've said. The chronic high nitrates prior to the riparian's saw me changing 50% twice a week! And that only kept it down to 40ppm! The WC's stress is definitely unwelcome, I agree. I imagine the nitrates in the supply is very inconvenient. I'm lucky as insofar as the resolution of a liquid test is concerned, I cannot measure any nitrates in our water supply (it must be there but it's low enough to not be detectable with the API test kit). I too had a PH buffering issue though where I'd see swings as high as 0.5 in a day but crushed coral seems to have eliminated that fluctuation completely. If 7.4 is a good PH for you, (the PH coral dissolves up to) that definitely worked for me.

Sunnyspots said:

This is really interesting to me as I had noticed, despite high tap water nitrates, my tank water has been lower; 5 at the last reading. I have a reasonably well planted tank, although they are all new and not well established, but have plenty of Salvinia which grows like wildfire. So now I know that is where my nitrates are going. I knew plants used nitrates, but not to that extent.

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There is a bit of confusion here. Terrestrial plants and aquatic plants are different with respect to their preferred/normal source of nitrogen. The plants described in @dasaltemelosguy post #5 are terrestrial plants, and they will take up nitrates as their preferred source of nitrogen. I've no idea if other forms (ammonia/ammonium, nitrite) are or are not possible sources for terrestrial plants, but nitrates is certainly basic. This is why fertilizers for garden and house plants contain nitrates--and the following will explain why such fertilizers should never be used in the aquarium.

Aquatic plants such as those we use submersed in aquaria prefer ammonia/ammonium as their source of nitrogen. Most species will not take up nitrates unless forced to, and by this I mean that if the light (which drives photosynthesis) and the required nutrients are available, and ammonium is exhausted, the plants will then turn to nitrates. This requires extra energy from the plants because they have to change the nitrates back into ammonium, and apparently it takes the plants approximately 24 hours to "change gears" so to speak. This is what occurs in natural or low-tech planted tanks, where the light and other nutrients will not be anywhere close to the level that will cause the plants to need to uptake nitrates, and they can use a lot of ammonia/ammonium especially if they are fast-growing species such as floating plants. This is why many refer to these plants as "ammonia sinks." But in high-tech planted tanks with brighter light, diffused CO2 and daily (or more frequent) nutrient fertilization, plants will turn to nitrates once the ammonium is no longer sufficient for their needs.

The reason aquatic plants reduce nitrates in a natural/basic fish tank with plants is because their rapid uptake of ammonia/ammonium out-competes the nitrifying bacteria/archaea, and with plants this does not produce nitrite, which in turn means much less nitrate. This of course involves the nitrates that occur within the biological system of the aquarium. Nitrates occurring in the source water added at water changes is a very different matter. And I have no idea why nitrates would reduce as you mention; there are species of anaerobic bacteria that live in the substrate and use nitrates, but I have not delved into this in any detail.

VERY interesting and educational, thank you. Could one then surmise, or is it probable that in a healthy, fully cycled, closed aquatic system, that there would be no ammonia or ammonium available so the nitrates would then be the only food source, hence the dramatic reduction? I found little or no benefit in nitrate reduction when I tried to breed anaerobic in a separate filter, about 6L of pond media, even after many months. Within about 2 weeks the nitrate reduction was dramatic with riparian's as shown in the images. Of course I'm comparing apples and oranges as I have no way to quantify how much of an anaerobic colony I had, nor how much I'd need!

dasaltemelosguy said:

VERY interesting and educational, thank you. Could one then surmise, or is it probable that in a healthy, fully cycled, closed aquatic system, that there would be no ammonia or ammonium available so the nitrates would then be the only food source, hence the dramatic reduction? I found little or no benefit in nitrate reduction when I tried to breed anaerobic in a separate filter, about 6L of pond media, even after many months. Within about 2 weeks the nitrate reduction was dramatic with riparian's as shown in the images. Of course I'm comparing apples and oranges as I have no way to quantify how much of an anaerobic colony I had, nor how much I'd need!

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If I am reading this correctly...you had terrestrial plants and they use nitrate, so naturally they will remove it from the water; the nitrates get taken up from the soil (on land) in the water and the plant roots assimilate the nitrate from the water. In your situation, the nitrates in the water were/are taken up directly by the roots of terrestrial plants.

With respect to the aquarium situation, with aquatic plants...most of us have enough fish in an aquarium to provide an endless and sufficient supply of ammonium for the plants. Fish produce ammonia via respiration of course, and there is more occurring from the decomposition of organics in the substrate. In most of our tanks, with fish and plants, assuming it is not a high-tech system, there will be plenty of ammonium available to balance the other 14 required nutrients and light. Aquatic plants therefore have no need to use nitrates, and they do not (in this type of system).

That makes sense. My aquarium is currently very lightly stocked, especially after I had to remove the gouramis for aggression. It also has a fair few plants and 'passive' CO2 from an upturned plastic bottle. Maybe they have resorted to using nitrates whenever the ammonia has gone? It sounds a lot like the human body switching to using fats once all 'easy' sources of glucose have gone.

Sunnyspots said:

That makes sense. My aquarium is currently very lightly stocked, especially after I had to remove the gouramis for aggression. It also has a fair few plants and 'passive' CO2 from an upturned plastic bottle. Maybe they have resorted to using nitrates whenever the ammonia has gone? It sounds a lot like the human body switching to using fats once all 'easy' sources of glucose have gone.

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I won't speculate on this. But it is a question of all 17 required nutrients being available (in sufficient quantity) and the light being sufficient to drive photosynthesis. Aquatic plants seem very reluctant to use nitrate, so everything else has to be there before they will expend the energy to do so.

Alternatively then, my tap water is currently low in nitrates (it can vary a fair bit). It seems unlikely all the nutrients are perfect. What a shame if that's the case. I've been desperately looking for a way to counteract high nitrates in my tap water since, according to the water board, they go up to 16 mg/l.

Would water storage in a separate vessel work for you? Or adding a Refugium?

You could add nitrate loving plants in such a vessel such that it would, over a period of a week or so, would basically remove them from that stored water. More or less the plants will grow as much as there are nitrates to support it so it's in a partial sense, self regulating.

Many people use ROI and add supplements for the plants and minerals for the fish. An ichthyologist and marine biologist near me (here in Los Angeles) who run the LFS do the latter.

Sunnyspots said:

Alternatively then, my tap water is currently low in nitrates (it can vary a fair bit). It seems unlikely all the nutrients are perfect. What a shame if that's the case. I've been desperately looking for a way to counteract high nitrates in my tap water since, according to the water board, they go up to 16 mg/l.

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Source water nitrates have to be dealt with outside the aquarium, and some members here have had this issue and solved it. I know @AbbeysDad is one, so I will include him and I am sure he will provide the info.