High Nitrite!!!!!

[twestacott]

My 36 gallon has been running for about 2 months and suddenly the nitrites have been getting high (3-4ppm). Tha ammonia is 0 and nitrates are around 5. I just did a 50% water change got the nitrite down to 0.5 with the Nitrate still around 5. Is this a mini cycle or could it be from overfeeding. I feed once a day about a dime size of flake (there are 4 zebra danio, 6 neon tetra and 3 cory cats).

Any advice will be greatly appreciated

 

[jlk]

It doesnt sound like overfeeding if you are only feeding once a day. Did you do anything different recently such as a heavy gravel vac/over-zealous cleaning or replaced filter media or overly-cleaned filter media or cleaned it all at one time? Over doing cleaning could have removed some of your bb. Have you checked the ph in your tank as well? Ph changes are enough to upset your tanks balance. Your amm>nitrite bacteria are still working well so you will just have to stay on top of your testing & water changes until your tank re-establishes itself. We just need to figure out why this happened so it can be prevented in the future.

 

[twestacott]

I do gravel vac with every pwc. Other than that no cleaning of the filter media

 

[jlk]

I would only grav vac 1/2 your tank at a pwc then the other half with the next pwc. How does your ph look? Are you adding anything to the tank other than water conditioner? Have you added anything new or changed decor recently?

 

[twestacott]

Nope havent changed decor at all and am only adding Prime for dechlorification with water changes. PH is sitting around 7.5

 

[jlk]

Any new fish recently (past few wks)?

 

[twestacott]

About 3.5 weeks ago we added 6 tetra and 3 cory cats

 

[jlk]

Well, that makes sense. Your bioload increased. The amm>nitrite bacteria have already adjusted upwards to the increase but the nitrite>nitrate bacteria typically take twice as long. Just stick to light gravel vacs & continue to monitor your water parameters & do water changes as needed to keep levels in check. Things should be back to normal soon! I would be a bit more conservative in the future when adding fish (ie- just the tetras or just the cories but not both groups at the same time) to avoid possible spikes.

 

[twestacott]

Ok thanks. We only plan to add 5-6 fish ata time from this point on

 

[twestacott]

Tested again tonight. Nitrites are back up around 1.5-2.0 ammonia is 0 and Nitrates around 5.0. Do I do another water change?

 

[jlk]

Yep, you want to try to keep those nitrite levels under control until things stabilize.