go to planet catfish and check up channel, there is a certain number of rays in one of the fins, and that is the best way to identify a channel catfish.
It's not a channel catfish. Channel catfish have forked tails, that fish does not. It is a bullhead, IMO it looks like the spotted bullhead (Ameiurus serracanthus). Lovely fish, would love to keep one of them in aquaria someday.
What is the current temp in the tank? Being from Florida I'm sure any bullhead you catch are quite used to warmer water. Upper 70's should be fine. Make sure your current fish are larger then the bullhead though, bulheads will try to eat just about anything they can fit in their mouths.