i originally kept fire eels with my gar, and they where in the tank first. the 2 guys i have now are fairly aggressive eaters and have been bitten once or twice. ive actually seen my cuban make a grab for the same worm my eel did and end up biteing the eel, who turned around and bit back. and everyone is fed very well. at one point i was concerned about the smaller eel but he holds his own and otherwise hides under the DW if things get to crazy. imo the key is keeping the gar fed and giving the eels hide spots that are more hassle then worth poking around in. but my gar have always had spineys as tankmates.