Low pH/KH, fish stress, what to do?
I have a (~5yr old) 37gal that has a DIY CO2(Hagen canister). Lately, I have been noticing a pH drop all the way from 7.2 to 6.2 over about 2 weeks. My KH is currently 3 deg and my drop checker is reading adequate CO2. My fish are looking very stressed as well.
I'm really concerned about this and would like to get the pH back to ~6.8/7 but I'm not sure how to go about this. Would raising the KH with baking soda help me out or am I way off base? Any help or suggestions would be greatly appreciated.