I agree that the kribs(P. pulcher) will get too mean during breeding. The P. taeniatus are a much mellower cousin, I have 2 pair( less than2") in a 20 atm and there are fry in there too. Also you could try one of the Laetacara's( thayeri, dorsigera, curviceps). I know that msjinkzd had some dorsigera a couple weeks ago, and i saw the other two on AB this last week. There is also Anomalochromis thomasi(african butterfly cichlid) and Pseudocrenilabrus nicholsi ( nichols dwarf moutherbrooder). All species would do great in a planted. The last 2 are African riverine, and I have seen both on AB in the last couple of days. The keyholes would be awesome looking in your tank though.