Honestly, I wouldn't recommend either fish for beginners. I kept large specimens of both species, and a fine balance had to be kept up. Tank arrangement, feeding, light schedules, etc. Not saying that you are a beginner, just that the bgk especially needs some special care. As for tank mates, I would recommend a larger, slow moving peaceful cichlid. Severums, uaru, angels, the like. The problem with the polys and bgk is they are both very slow eaters. Both fish are mostly blind and have to sniff out their food. Things like silver dollars will out compete them. On the flip side, things like neons and other small fish will simply be eaten. Plecos are a good option, but that introduces more competition for territory.