I have a fire mouth cichlid in with my 2 gar, and its doing fine. I originaly had two of them in there, but the larger one was getting very territorial, at first it left the gar alone cause they are bigger then it was, but after awhile it learned the gar dont really fight back and it started nipping at them, so i threw it into another tank by itself and left the small one.
I also have 2 clown loaches which do fine, when i first put them in one of the gar bite it in its mouth, and then relised it couldnt swallow it, and hasn't bothered them since, the fire mouth cichlid will chase the loaches abit here and there but they dont seem to care to much anymore. So cichlids can work but if they are to small they will likely get eaten, and to big they might get territorial.