Any antibiotic will wreak havoc your Biofilter or at least limit its capacity to regain "full power". As all your fish stopped eating it´s sure an environmental problem, the signs of bacteria you mention are the result of poor water quality so improving it MUST make them more comfortable and able to ...

Rob, Hope this might help: Continue with the water changes with conditioned water: aerated for 24 hrs (at least) to improve O2 and let CO2 from your source water to be vented. Lower the ph in the new water at 6.5, aiming to reach a ph of 7 after a few more 30% water changes. First I´d concern about ...

Does anyone knows what are the main minerals needed to "reconstitute" RO water, DI removes Ca and Mg.
How do sensitive catfish react to RO vs DI vs tap water? Is there a "catfish happymeter" besides EC or pH?

Anyone familiar with the balling method, a 2 part recipe for replenishing Calcium and KH to reef aquariums. Might work if using very little for reconstituting minerals lost by DO.