yeah, but kribs probably wouldn't do well in a 20 hex, which is narrow and high and won't provide male kirbs any room to establish territories.
Try a pair of dwarf blue rams. They are a cichlid, are very beautiful, and don't get very big. From what I understand, their breeding requirements are very specific, so they won't go breeding bonkers in your tank.
Personally, in a hex, I would nix the whole cichlid idea and simply go with a nice small school of colorful tetras. Hexes really are not appropriate shaped tanks for territorial fish.
~~Colesea