Join Date: Jul 2014
Location: In the hills of Eastern Kentucky, USA
First how old is this tank, how long set up?
Fish can survive a wide range of PH and most fish, unless you had an importer order your fish for you those fish were propagated here in the states most likely.
I have read that CO2 injection can bring your PH down, and you did say you had CO2 right.
Sounds to me like you have something else going on there. What are the other water parameters? Ammonia, nitrite, nitrate?