Started to cycle the tank the weekend after Christmas. All was chugging along fine and then pH started dropping, very slowly at first. I know that pH fluctuates quite a bit during tank cycling, so I didn't think anything of it. Then, last week, just as nitrite levels were starting to drop, pH started dropping significantly. I'm talking started at 7.6 and was down to 6.4 in a matter of a day or two. I did a 50% water change to try and get the pH back up, and it helped a bit (brought it back up to 7.2 or so). Within another day or so, pH was down again in the 6.2-6.6 range so I did another water change, this time a large one, doing about 70%. The pH returned to about 7.4 but now, only a day or so later, the pH is down to 6.2 and I'm going to assume that it will continue trending downward. The other strange thing is that whereas ammonia was dropping from 4 ppm to 0 in about 8 hours, it's now only down to 1 ppm after about 12 hours. This tells me the cycle is stalling, and I'm thinking it's due to the significant pH drop as I know that if pH gets too low for too long the ammonia conversion process can change (ammonium rings a bell).
What to do?? It's clear to me that water changes aren't helping (tap pH is right at 7.6). I tried to add a pH buffer (only affects pH; doesn't have any other properties according to the box) but that didn't seem to help at all. Should I lay off the ammonia dosing for a few days to see if pH bounces back, keeping ammonia down to 1 ppm or so, so as not to kill off the bacteria colony?
What to do?? It's clear to me that water changes aren't helping (tap pH is right at 7.6). I tried to add a pH buffer (only affects pH; doesn't have any other properties according to the box) but that didn't seem to help at all. Should I lay off the ammonia dosing for a few days to see if pH bounces back, keeping ammonia down to 1 ppm or so, so as not to kill off the bacteria colony?