# Please help: Nitrate won't go down



## hypersushi (Jun 6, 2005)

Recently, I had a few rummy noses dying due to internal bacteria. The rest of my fishes are fine. Those bodies that I could find, I promptly removed. I did water tests and found ammonia to be negligible. Nitrite is zero but Nitrate is about 20 to 30 ppm. I verified if the test kit was faulty by testing against the tap water and also RO water. It gave negligible readings.

My tank is a 4footer with about 3WPG, fairly densely planted stems plants (majority). Fuzz algae is appearing on my Blyxas and Tiger Lily and some BBA is growing on my gravel and equipments. CO2 is about 32ppm. Lights are on 8 hours per day. The plants are pearling normally.

It's been a few days now and everytime I test for Nitrate, it's around the 20ppm mark. I'm afraid to dose KNO3. Aren't plants voracious eaters of Nitrate? How come the levels never seem to drop? (It's been three days now)

What could be the reason?
1. There is a dead fish rotting away but the nitrifying bacterias are efficient enough to break ammonia and nitrite down to nitrate fairly quickly?

2. Plants are not absorbing the Nitrate fast enough. Something is limiting (but what???)

Apart from doing a WC, what else can I do? Will pouring those Ammo Guard solutions help?


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## mrbelvedere138 (Jan 18, 2006)

While I can't pin the cause of nitrate, it is often difficult, I can suggest a solution:

Duckweed. Lemna minor.

Float some, it should control any and all excessive nutrients.


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## Salt (Apr 5, 2005)

How many fish, snails, shrimp, etc.?

Usually nitrates that don't go down are the result of high stocking.

I regularly see a lot of posts talking about how "plants absorb nitrate," are "nitrate sponges," etc., but that's only applicable at light to medium stocking levels at the most. Even a tank with an *extremely* high plant mass will not be able to lower nitrate if the tank is full to overstocked.

I have a vastly overstocked 42 gallon hex (a problem I'm currently working on remedying). I added an anaerobic bacterial nitrate filter to the tank a couple of years ago, which keeps nitrates around the 30 ppm mark. Without it I'd probably easily be over 100 ppm. That's all with weekly 40% water changes with nitrate-free water.


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## Tonka (Mar 20, 2004)

I know that you calibrated against tap and RO, but testing for zero nitrates is not the same as testing for the existence of nitrates. Having your nitrate test kit show the same value for nitrate regardless of nitrate concentration is THE indication that your test kit has gone (or has always been) bad. There is no shortcut for testing with a standardized solution.

OTOH, even though I'm sure that your test kit has gone bad, you will still neeed to prepare a standard solution to test your new kit, so you might as well test your old one before throwing it away.

BTW, 20 ppm NO3 should not be causing problems in your tank.


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## Squawkbert (Jan 3, 2007)

Find the bodies.


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## hoppycalif (Apr 7, 2005)

Do you dose phosphates? Plants won't use much of the nitrates if they don't get phosphates too. I agree with Tonka that 20 ppm and more of nitrates won't kill the fish. Also, I agree that you need to calibrate the nitrate test kit if you are going to depend on it. But, I'm betting that you can add some phosphates and the nitrate level will drop drastically.


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## Glouglou (Feb 21, 2006)

*Nitrates not absorbed*

You probably have a dosing routine for 6 months or a year, dosing No3 and everything else. Nitrates was absorbed by plants and you as a good gardener you feed them well.

Plants can make a reserve of nutrients they don't used (in excess) in the case of Nitrates they have a reserve factor of 1000 times what they need.

When the plant fill is reserve and nitrate is still distributed at the same concentration you reach saturation. The plant cannot process the nitrate in dissollution and the monting level of nitrate can cause others nutrients problems.

Just forget the nitrate dosing, the plants can go for week on their reserve. Monitor the nitrate in your aqua when it start to go lower (not due to water change) your plants are processing the nitrate again. Go ahead with light dosing at first and test, you should find a kind of balance that is unique to your setup.


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## BryceM (Nov 6, 2005)

BTW, an extremely high light tank with a thick plant mass, very few fish, and ample CO2 won't drop nitrate levels by more than a few ppm per day. Under less ideal circumstances I wouldn't expect to see a downward swing for quite a while - maybe a week or more. 3 days is nothing.

BTW, "32 ppm"?????? How do you know this? It is nearly impossible to measure CO2 accurately. My guess is that you actually have much less CO2 than you think, especially if you're having the BBA and other algae issues you mention.


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## ruki (Jul 4, 2006)

mrbelvedere138 said:


> While I can't pin the cause of nitrate, it is often difficult, I can suggest a solution:
> 
> Duckweed. Lemna minor.
> 
> Float some, it should control any and all excessive nutrients.


Giant duckweed, Spirodela polyrrhiza, works a bit better for me. The roots are more significant and there is more air contact with the leaves. And it's easier to keep this under control 

For higher light tanks, water lettuce works even better.


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## Salt (Apr 5, 2005)

Squawkbert said:


> Find the bodies.


??


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