i have a river tank set up with bluegills, a channel catfish, a small bullhead and a crayfish. i want more fish in my tank but not sure what would get along with my current residents. Any suggestions?
channel cat will outgrow that tank in no time. The rest of your stock should be okay though for now, that crayfish's days are numbered though he'll be a snack for one of the bream or catfish sooner or later
If you have a few of each, then you already have too many fish for a 55. Bluegill can end up around 8-10" and a single channel cat is WAY too much for a 55 in the long run