Go planted and get some White Cloud Minnows (for unheated tank). If you want a type of Dwarf Cichlid...Apisto are the smallest I can think of and I think they need more than 6g. It's best to just do a small planted community tank with this one. I had one set up for awhile with Java Ferns, Anubias, Dwarf Hair Grass, and Wisteria, but broke it down in Spring. I still have it, but I was going to give it to a friend.