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Nitrite AFTER WC


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Hi Aquarists - i tried searching but couldnt really find anything. i also looked all over the web but wanted to see what everyone here thinks. I have a new 37G tall tank that has been running for about 2.5 months now. It was fully cycled a few weeks ago, 0 ammonia, 0 nitrite,10-20ppm nitrate. In that time, I have done 2 wc. The first was about 2.5 weeks ago and was 25% because my nitrates were 20-30ppm. This brought my nitrates down to 10ish. nitrates started to creep up again to 40ishppm which is why i did a ~35ish% wc. this brought nitrates down to 20ishppm. today im seeing 1ppm nitrite 0 ammonia 50ishppm nitrate. i have not gravel vac or cleaned my hob since setting up tank. 

im thinking its my HOB?? i need to clean it?? but its only been about 2.5month with very light population. any thoughts?? thank you!!

current population:

4 amano shrimo

6 neocard shrimp

3 nerite

3 dwarf red platy


8 jungle val

8 stems of pogo

1 java moss

4 stems of ludwiga rp


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I probably wouldn’t clean the filter at this point since you want to have as much beneficial bacteria as possible. There are two kinds of BB, one converts Ammonia to Nitrite and one converts Nitrite to Nitrate. The second type apparently needs more time to develop. You can do another water change and then feed very lightly until you see Nitrites drop back to zero. You can also add Seachem Prime to detoxify the Nitrite while you’re waiting for the cycle to catch up.

On 3/1/2022 at 2:32 PM, coldwater said:

actually as i write i did just add a several aco root tabs and the 40G amount of easy green. maybe thats poping up my nitrates and nitrites? ill give it another couple of days and see what happens...sigh

You’ll see a rise in Nitrates from those but not Nitrites. My guess is that the BB that convert Nitrite to Nitrate are still developing. Since you have some fish and inverts you’ll need to do water changes and keep a close eye on parameters until Nitrites reach zero. 

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Nitrite oxidizing bacteria are extremely sensitive to almost any sudden, small parameter change, including from water changes, for 2-3 months after cycling. The spikes usually last only a day or two and won't hurt your fish unless they get really extreme or don't go away.

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