I have a problem for about 2 weeks now.
My tank has long been established with no problems. I test Ammonia, Nitrite, Nitrate, Cl, KH, GH, pH two times a week.
Lately I am getting 0.3mg/l Nitirite. 0 Amoinia, 5ppm Nitrate. THis is usual except for the Nitrites, which are always 0. It does not go down no matter what I do. I first noticed it when I saw my neons gasping for air, I put in extra Prime (what the label indicates for Nitrate emergency, I think 10x concentration) and the neons calmed down. I added Biozyme, still no go. I added Cycle. Will not drop.
I use a Magnum 350 and Fluval 304 on my tank (60 gallons) so I think I have enough filtration. I can add another 304 I have if needed (just needs some new tubing). But I don't think that can be the case.
Can the biofilters die off even if you don't touch the filter? What I mean is I only change out the first chamber (filter floss) every 8 weeks or so and rinse the prefilter foams out at the same time in dirty water. I am very careful not to hurt the filters, but can they die off on thier own? I don't touch the ceramic noodles, when I open the filter, first thing I do is transfer them to another container of siphoned tank water. They are out of the filter max 15 min.
I add Melafix, Prime, and Flourish Excel as directed on the labels on each water change (33% weekly). Could any of these be culprits (but I use them all the time)
The fish seem happier since adding the Prime, but the Nitrite has not fallen to 0. It was always at 0 before. Nothing has changed (no new water source, no new fish, no extra food, etc)....and I didn't catch any ammonia spike earlier.
After one week, I did 50% water change, immediate test results after = 0.3mg/l Nitrite...
Is there anything that can add Nitrite to water? Even my Nitrates aren't rising...something is terribly wrong I can feel it. No fish have died yet, but had I not noticed the neons gasping that one morning, it could have been very bad.
Thanks for any help you can give.
One last note: I just remembered I had Discus eggs back then....maybe something in that. I added a small amount (about 1/2 recommended dosage) of Maroxy to help prevent fungus on the eggs (they didn't make it). Could this be it?