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Discussion Starter · #1 ·
I converted my 10 gallon to a NPT about 10 days ago. About a week ago I managed to turn the filter off overnight, so had to do the planned transition rather faster than I wanted to. Still, all seemed well.

But lately, I'm getting nitrite readings in the water. Nothing higher than 0.25ppm, but still definitely there. There is no ammonia, and the nitrate is about 7ppm. The plants are growing, but I wouldn't say they have taken off yet.

The tank is planted with hygros, a sword, a crypt, java moss and duckweed. Current stocking is low compared to my earlier stocking of this tank (a betta, 4 white clouds, 4 small corys). One of the white clouds seems ill (she is swimming bent), and I don't know whether this is connected to the trace nitrite or to something else.

This morning, a few hours ago, I added an airstone to the tank, to see if this would help. Adding an airstone sorted out the problem with nitrite in my 5 gallon a few weeks back, but today, so far, it isnt making any difference. There is also a small powerhead/filter in the tank, with a cycled sponge in it. The filter is for circulation - it is rated for a 13 litre tank, so it shouldn't be providing significant biological filtration. I was hoping the plants would be doing that already.

Where is the nitrite coming from and what can I do, other than water changes, to stop it?
 

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Perhaps there is nitrite because there is not enough oxygen for the nitrifying bacteria so it's using the nitrates instead. I don't know if you would notice any difference in the nitrites in only a few hours of adding an airstone though.

Also, it's only been 10 days since you've set this tank up. My 2.5g took almost a full month to finally cycle so it might just take a little more time.
 

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I agree with Red Rose. Every tank is different. Possibly nitrate fertilizer were present in the soil you used. A gentle airstone will speed up bacterial processing of excess nitrogen.

One effective method that pond hobbyists frequently use to counteract nitrite toxicity is to add sodium chloride (physiological fact: chloride ion competes with the nitrite ion for uptake by the fish's anion transporters). You can add one to two level teaspoons of ordinary table salt to your 10 gal tank. This level, which I calculated to be between 0.015% and 0.03% NaCl, should easily protect your fish from 0.25 ppm nitrite and not harm the plants.
 

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Discussion Starter · #4 ·
Thanks both, I guess I'll do water changes and try to be patient. It is worrying when a fish is sick, though.

I already added a little salt, so the nitrite shouldn't be harming the healthy fish too much. It's the sick one that I'm worried about - she's sticking close to the bottom, and her spine is bent into a wide, upside down, "v" shape. Not good.
 

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When my betta's tank ended up with both ammonia then nitrite, I had a separate tank to put him into so waiting wasn't that bad. Even though I had a small tank for my guppies to wait in when their 2.5g ended up with ammonia and nitrites, the wait was much longer because I didn't air out the soil like I normally do and the ammonia spike caused my guppies to end up with Ich. If you have something that you can put your 10g's inhabitants into for now, I'd move them so they won't get sick or if they are sick because of it, this will give them a chance to heal up.

I plan on getting another tank for my guppies because of a slight leak in the one they are in now and all I know is that I'm letting this one sit and take it's time before I add any living creature to it. After what my guppies and betta went through, I now know why some people choose to wait until things establish before adding fish, snails, etc. to the tank.
 

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Thanks both, I guess I'll do water changes and try to be patient. It is worrying when a fish is sick, though.

I already added a little salt, so the nitrite shouldn't be harming the healthy fish too much. It's the sick one that I'm worried about - she's sticking close to the bottom, and her spine is bent into a wide, upside down, "v" shape. Not good.
There are so many diseased fish being sold that I would not attribute this fish's problems to nitrite. Also, bent spine can be due to many factors, even injury or nutritional problems. I wouldn't correlate one fish's problems with the 0.25 ppm nitrites. If you've already added a little salt to this tank, good! You've basically taken care of the nitrite problem.
 

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Discussion Starter · #7 ·
The sick fish died after about 4 days of being bent in her spine. I suspect that the stress of me changing the tank substrate and moving the fish about in the process triggered the problem, though what it was I don't know at all. I ran a UV sterilizer on the tank for a couple of days to reduce the bacteria in the water, but didn't seem to make any difference to anyone, so I stopped it.

The other fish are healthy.

The plants are growing like crazy.

The nitrites have gone and I am gradually turning down the airstone in the tank, since I don't want it there long term.

Thanks for the advice.
 
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