# causes for persistent trace nitrite in NPT



## helenf (Mar 24, 2008)

I have had trace nitrite (less than 0.25ppm) in my 5 gallon NPT for a couple of weeks now, on and off. I just noticed it was back, so am wondering about it.

I also have just gotten Diana Walstad's book in the post, so reading it now. I got to the section about bacteria turning nitrate into nitrite and now I wonder whether that is the source of the nitrite in my tank, rather than food->ammonia->nitrite, as I assumed. 

Here's the things that have happened in this tank recently. The tank is now about 2-3 months old, and is stocked with guppies, a baby siamese algae eater, a betta and an apple snail.

- I had lots of fungus growing on the bottom, plus hair algae growing on the plants. On advice I added an airstone. The fish got more active immediately, and the fungus disappeared within a few days and has not come back. 

- I added the SAE into the tank, temporarily, to control the hair algae on the plants. He seems OK but the tank is too small and I'm planning to move him out to a larger tank soon, as soon as I get some shrimp I ordered that apparently eat hair algae. 

- I bought the apple snail to eat leftover fish food and keep the bottom of the tank cleaner. in 3 weeks he's more than doubled in size, I think. Amazing growth! 

- then I noticed a lot of pond snails hatching. I never had them before, so wonder whether the increased aeration has made them hatch. I'm having trouble controlling them, despite siphoning out hundreds of the little things. If they all grew up the tank would be nothing but snails!

- I noticed nitrate in the water a couple of weeks ago. It was zero when I set the tank up, then for a few weeks I was adding nitrate to the water, because I was worried the plants wouldn't have enough food. But I stopped that on what seemed like good advice, and the nitrate fell to zero, but now it seems to be settled on around 5ppm. 

- so I got a female betta, hoping that she would eat the pond snails. So far she doesn't seem interested, though I've been told that some of them do eat snails or at least their eggs, so I'm hoping...

- I am not feeding the tank any more than I ever did, so there is no more food going into the water, even though there are more fish than before. I think that means that the bioload should still be OK for the tank. The plants are growing fast and I never measure any ammonia in the water. I didn't get any nitrite at all for weeks, while feeding at the same level.

I'm basically wondering whether the extra aeration I've added to the tank is having some effect that is causing the nitrite to rise. I'm also wondering why the plants and bacteria don't seem to be controlling the nitrite level. Is there something I could do to tip the balance back so I don't get this nitrite reading? Is my feeding the tank a source of the nitrite, or is it unrelated? 

Any suggestions?


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## bratyboy2 (Feb 5, 2008)

every walstad setup has its time...but yours should be well over.
first question to better understand this would be how many babies do you have in there and how big are they?
second what kind of plants do you have?
how deep is the soil?
and how are you providing the oxygen?
if your wanting the snails to go you could try a small dwarf puffer..
really you need some fast growing plants if you dont have them. you could try some floaters for sure...those will help alot.
5 gallons can be really hard to control and i give you alot of props for attempting this. i myself did a 5 hex and had good luck with some fish in it. i did screw up with the floaters and the fast growth plants though by not having enough.
so let me know on the questions above and we will go from there to help yah more bud! good luck!


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## helenf (Mar 24, 2008)

Thanks for replying. I am pretty sure that the nitrite doesn't come from the soil directly, because the first couple of weeks I had water in the tank, there was no ammonia, nitrite or nitrate at all. I think the nitrite is coming from some process that has gotten out of balance recently. 

To answer your very sensible questions:

- the tank is 5 gallons, with about 1 inch of soil, topped with 0.5 inches of gravel. 

- it's been running, as I said, 2-3 months and is mostly doing alright. I'm happy with it, anyway 

- current fish load is: 
about 8 endler/wild guppy males. They are much smaller than normal fancy guppies - I make them at about 0.5 inches long 
1 female betta about 1 inch long
1 apple snail (bridgesii) about 1 inch long and growing really fast (he has doubled in a couple of weeks)
1 baby siamese algae eater, about 1.5 inches long
countless baby pond snails about 1-2mm long, which I am removing as fast as I can find them

- current set of plants are
anubias nana - growing slowly
some kind of green crypt growing like mad - I can see it taking over the tank sooner or later
hygro 
hygro difformis (nearly but not quite emergent)
some other kind of larger leaved hygro, not sure what it is
duckweed
azolla competing with the duckweed
pygmy chain sword that isn't doing too well but I hope it'll pick up

Some of the hygros have lost lower leaves but are growing upper leaves just fine. Everything else is growing. The duckweed and azolla cover all of the surface except a small feeding ring I keep clear for feeding and for the betta to breathe easily, and that's with feeding the goldfish in my other tank some duckweed most days, so it's growing fast too. 

Don't dwarf puffers get agressive with other fish? Admittedly I hadn't thought of one of those. 

Anything else I can tell you to help you to help me?


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## helenf (Mar 24, 2008)

Oh, I forgot to say that the oxygen is provided with an airstone. Not running very fast - I am trying to gradually turn it down, now that the fungus problem is solved, and try to see whether I can live without it or not. If the fish get slower or less hungry without it I'll certainly put it back, though.


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## Red_Rose (Mar 18, 2007)

Both of my tanks when through nitrate respiration when they were first set up but that was because there wasn't much oxygen in the water so the bacteria used the nitrates instead, causing nitrites to appear.

I still have nitrates in my 2.5g but I don't have any nitrites. To be quite honest, I don't know why nitrites would still be showing up in your tank. Have you taken a sample of the tank water to a LFS to get it tested? Perhaps it's your test kit that's giving you an inaccurate result.

bratyboy2,

Why and how would 5 gallons be difficult to control? I know it's more difficult to keep a cycle going in tank under five gallons but that's when only a filter is being used and not plants. Granted, it took quite a bit for my 2.5g to finally settle but it did and everything is growing very well and the guppies are happy.


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## helenf (Mar 24, 2008)

I tested the ammonia and nitrite a couple of hours ago. Ammonia 0, nitrite higher, up to 0.25ppm, or nearly so.

And this is with less feeding the tank than before, since I'm worried about this nitrite thing. And I've been putting the light on for longer, in an attempt to get the plants to suck more ammonia and nitrite out of the water.

I did turn the airstone down the other day (not off, just down a bit). I'm trying to gradually remove it from the tank, since it's done it's thing of stopping the fungus on the bottom, and I read in Diana W's book that it might be driving off CO2 produced by decay of organics on the bottom. Anyway, I've just turned the airstone back up to full and will see if that seems to help.

I've also added some more plants to the already heavily-planted tank. More things consuming nitrogen can't hurt. 

Please, does anyone have any ideas about this? I'm worried and confused about it, and these nitrites are starting to get to a level where I'll need to do more water changes if they don't go down in a day or so. 

My test kit (API drop test, only a month or so old) shows 0 nitrite for all my other tanks, so I doubt that it is wrong just for this tank.


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## dwalstad (Apr 14, 2006)

Glad to hear the fungus went away. Your tank at 2-3 months isn't that old-- or too old to have nitrite. Please forget about adding nitrogen fertilizers to your NPT; this may have caused the problem. But don't worry, eventually, the excess nitrite in your tank will cycle through and be gone.

Persistent nitrite at 0.25 ppm will stress fish, and you could end up with diseased fish. Therefore, I would change the water and try to keep the nitrites at or below 0.05. Temporarily changing 2 gal of water once or twice a week in a 5 gal tank should be no big deal. Folks, here is the great advantage of small tanks! 

For now, I would relax about the snails. They just may not be the size that the fish want to snack on yet. I can assure you that not all those little snail babies will grow up! Since this tank had fungus and an excess of debris, these snails might be helping clean up the tank. Once they're adults, you can easily get rid of them by putting a dish with a little meat on it in the tank. The snail population will stabilize eventually. My 3 tanks have been going for years with at least 3 species of snails, but there's no excessive population.

You've had a few setbacks, but it sounds to me like your tank has most things right-- good plant growth, floating plants, soil, fish of appropriate size, and snails doing a lot of necessary housecleaning. Not bad.


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## helenf (Mar 24, 2008)

I'm no longer adding nitrate to the tank, and haven't done that for several weeks, once I became convinced by advice from this forum that it was unnecessary. However the background nitrate level, which was originally zero (why I was adding it in the first place) has now risen to 5-10ppm. I don't understand why. Would that be high enough to drive the production of nitrite from the nitrate? 

The nitrite level isn't persistently 0.25ppm and I will certainly do water change to keep it lower. But it seems to fluctuate anyway - now, a few hours after my last measurement of 0.25ppm, it is back down to a trace amount that barely changes the test kit colour. I just don't understand why it is getting elevated at all, especially after being solidly zero for several weeks at first. 

Being a scientist with a natural desire to understand stuff in general, I would like to understand this nitrite thing, if possible. It's bugging me!


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## dwalstad (Apr 14, 2006)

helenf said:


> However the background nitrate level, which was originally zero (why I was adding it in the first place) has now risen to 5-10ppm. I don't understand why. Would that be high enough to drive the production of nitrite from the nitrate?
> 
> The nitrite level isn't persistently 0.25ppm and I will certainly do water change to keep it lower. But it seems to fluctuate anyway - now, a few hours after my last measurement of 0.25ppm, it is back down to a trace amount that barely changes the test kit colour. I just don't understand why it is getting elevated at all, especially after being solidly zero for several weeks at first.
> 
> ...


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