Convict cichlids reach 6 inches, and a 20g is insufficient space for such a fish. While they may be small now, they will (or should) grow, and this requires space. A fish cannot develop internally if it is in too small (for it) an environment, it will be stunted with innumerable health problems.
A 4-foot tank, at least 55g, should be set up and then this would be a suitable fish. You can read more in our profile, click on the shaded name: Convict Cichlids.
If you are limited to a 20g long, and are interested in cichlids, there are some options. With basic and hard water, shell dwellers from Lake Tanganyika are one. If you have basic medium hard water, some of the dwarf cichlids from South America will work. Many more of these require very soft, acidic water. The Apistogramma genus contains many species, one of the most commonly available is the cockatoo Dwarf Cichlid, it is in our profiles too, click on the shaded name.
Last edited by Byron; 05-29-2011 at 01:40 PM..