Does anyone know of a cold water catfish that could live in aquarium? (not too large than) - the tank is 63 gallon.
(This is just a hypothetical question because right now the tank is still inhabited by tropical fish.)
We have a cold water catfish (Tandanus bostocki) in Western Australia but you can't get them anywhere else so if you don't live in Aust, you can't have one.
If it's just an unheated indoor tank, peppered corydoras do well in subtropical temperatures, and I think there are a few other sub-tropical corydoras too.
Stay away from hillstream loaches unless you are prepared to dedicate the tank to them.
I do not know the scientific name, but the common name would be Bullhead catfish. These guys grow to about 8 inches and are gluttons, they will eat everything.