Okay, a little background. (Sorry for the length...hope you hang in till the end) Back before Halloween I had a mass die off in my 46 gallon Rainbow fish tank. When I tested the water I found nitrites were sky high, so I did a few back to back water changes to try to save the remaining fish. The nitrites zeroed back out, and since my bioload was reduced so much, I restocked the tank hoping to salvage the cycle. So the tank only had a reduced bio-load for about 3 days. After restocking, ammonia started to spike. So after about a week of daily water changes I added a bottle of SafeStart. On day 14 I test...I have elevated ammonia. So after about another week of water changes, I try SafeStart again. 14 days later I test...still have elevated ammonia, but fish seem fine. So on it goes with partial water changes a few times a week until today when I get the idea that maybe I have ammonium instead of ammonia (hence the ammonia being elevated, but fish do not seem effected). So I test my water and sure enough pH is about 6.0 at best. I test my tap water and the water in one of my betta tanks and it's above 7.6 (as is normally the case). I hadn't tested the goldfish tank or other betta tank since I had just done water changes on them, so I wouldn't get accurate results. So now I'm stumped as to why the 46 gallon tanks' pH keeps dropping. The only thing different between my 46 and the other tanks is that the 46 is pretty heavily aerated and has a UV filter. Anyone have any thoughs on whats going on with the pH?