You could have to go with the smaller Royals like L204, LDA001, L002 are just a few that come to mind. You could try getting a 3-4 inch Royal and have it in there as well. Royals grow really slow so would take a long time to outgrow the tank.
This is not always the case. Cichlids are a huge group of fish some can be housed with pleco's others can not just do to there nasty dispositions. Also not all cichlids personalities match there species guidelines which we go by. You could get an oscar which won't hurt a pleco or you could end up with one that will harass it to death. Also not all pleco's should be kept in group due to territorial disputes between themselves.
You could have to go with the smaller Royals like L204, LDA001, L002 are just a few that come to mind. You could try getting a 3-4 inch Royal and have it in there as well. Royals grow really slow so would take a long time to outgrow the tank.
L002 is a tiger pleco(almost the same as a clown). They get just a little bit bigger
http://www.planetcatfish.com/common/species.php?species_id=735
Sunshines, Three Beacons, Vampires, Green or Blue Phantoms are all good starter plecos and easy to find...