when i used to work at the store we would usually recommend (finish reading before you go crazy and tell me im wrong i already know) angels, discus, osacrs, red tail cats, tin foil barbs, any tetras, any puffers, pictus, columbian sharks, iridescent sharks, and corys, and any barbs, or any of the rainbows, and most cichlids were ok. after actually learning i learned some loaches, angels, rainbows (but only the larger ones like tuquiose, boesmani, and red) the larger corys, and few cichlids. i know people have had success with some of the others but i would only recommend those with caution. also learned NEVER mix with pictus columbians, or iridescents as those prefer more brackish water or water with marine salt content and BGKs dont tolerate that well. i eventually "quit" because my information on compatability didnt sell fish well enough. to this day people still come in and ask for me and call for me.