I've had my 72 gallon community freshwater aquarium for a couple of years now and for the first time - last week, I began to have a problem with my nitrite and ammonia. I noticed several of my fish seemed to be gasping for air at the top of the tank, so I tested my water and found that my nitrite was around 4 ppm
and my ammonia was about 6 ppm
. Since I had just done a 1/3 water change and had cleaned the tank quite well, I assumed the problem was coming from my tap water. However, I tested the tap water and it seems fine. Since then, I have lost a few fish, and I performed several partial water changes, which initially lowers both the nitrite and ammonia, but they both keep creeping back up. I also lowered my PH
from 7.2 to 6.9, added some salt, and added phosphate remover, nitrazorb and activated carbon to my Eheim cannister filter, in addition to the Ehfimech, Ehfisubstrat and ChemiPure that was in there already. Now, the fish appear to be ok, but I just tested the water and I'm getting around 2 ppm
nitrite and 5 ppm
Since the problem began, I have been cutting down on my feeding and the number of fish has reduced from around 15 to 10 (so neither of those should be a problem at this point).
Any idea what could be causing this? Suggestions?
Thanks for your help.