Other options that would be cool but you'd have to be careful with would be to have a tank-with ONLY-a Convict Pair (that means 2 and only 2) or a Firemouth Pair. These fish are both recommended to be kept in bigger tanks, but if you can aqcuire an assured pair, you should be fine. You wouldn't be able to have any other fish in there at all, because these fish get very aggressive towards other tankmates when they are breeding, but you'd have a nice tank with lots of action, since Convicts and Firemouths are both active active breeders!
A great tank idea, but one that has to be carried out with caution and patience. Good luck!
A great tank idea, but one that has to be carried out with caution and patience. Good luck!