synodontist p has issues

[dmk6]

I just bought a tank off craigslist and it is great blah blah blah but. He had it stocked with 11 giant danio 1 pleco and a synodonist petricola i noticed when i filled it and got it running again that the ph was high 7.6 or so. when I cleaned up the filter I found a bag of some white rock like stuff and thought it was some kind of ammonia clean up stuff and threw it out but now i think it might of been something to bring up the PH. I checked my PH today and was all happy that it was 6.8 and was going about my buisness when i noticed the cukoo cat acting funny. So i did some research and it seems my little friend is from a lake in africa and requires a high PH. I don't know what the heck to do. the Giant danios can handle 6-8 PH I am not too sure about the Pleco I guess I can raise the PH and start a chiclid tank but i don't even know how to start and if the pleco and danios will be alright. One thing i can say is i am not into killing fish or even screwing something up as bad as this has been.

 

[toddnbecka]

Most likely the bag contained coral to buffer the pH, 7.6 is pretty typical for that. The Syno definitely won't like the acidic water, they're also very sensitive to changes in hardness. Simplest thing to do would be toss a handful of crushed coral into a filter or even into the tank. It will raise/buffer the pH gradually enough for the fish to adjust, certainly less stressful than lowering it so drastically was.
Otherwise, rehome the catfish to someone with a suitable setup and preferably more of the same species. They're social fish, much happier in groups than alone.