You could add most any shoaling fish, as long as they are non aggressive and aren't fin nippers. You don't want to get fish in there that get too big either, they will compete for food. You BGK will get anywhere between 8 - 10 inches but it will take it awhile. You can populate the tank with Rainbows, Gouramis(Dwarfs), Tetras(Not neons, I have Congos with mine), and most bottom dwellers. BGK are great fish but are delicate when it comes to water conditions so be careful.