I am starting a 20 gallon aquarium with 4 cory catfish and a betta. The tank is planted and has petco aquarium sand as the substrate. I put in the 4 cories and have just gotten the ammonia under control. When I tested the water though, it said my ph is at 9 which is WAY too high. In my other tanks, the ph stays at 7.5 so I have no idea what is wrong with my 20 gallon. Two of my cories already died and the 2 that are left are about to. They barely move and they haven't eaten in days. They're bellies look shrunken and though there's food right next to them, they won't touch it.
I'm thinking that I have to remove everything from the 20 gallon and start over. I will rinse the sand extra well in case it's leaking calcium or something. In the meantime, I'm thinking about moving my cories into a large plastic bucket. I will put the filter from the 20 gallon into the bucket to keep the ammonia under control. I am worried that the shock of going from a ph of 9 to one of 7.5 will kill the cories. They are about to die in the 20 gallon so I don't have a choice but to move them. Is there anything I can do to make the transition easier and possibly save my cories? Do you think it is already too late?