Cons, Kribs, auratus, brichardi, mannny mannny types. Alot of the lake Tang shell dwellers would be fine in a 20H imo. few other species as well. majority of fish that stay under the 6" range for cichlids would all be fine. I'de start w/ a group of juvies and let 'em pair off 'n get rid of the extras. a group of 5 juvies should be fine in a 20h until you get a deffinate pair. personally I'de stay away from Angels. You'de be talking alot of extra work. seperateing the eggs, fry tank ect.. majority of other cichlids make exellent parents. If your looking to do it for fun or food? also depends on suggetsions.