I'd advise against the fish. Cows should be kept by experience fish keepers, they are easily injured and get infections that are hard to cure. The jawfish are cool, but in such a small tank you will get very mad due to them constantly sifting sand and dumping it on all your corals. Try a clown goby or midas blenny. Gobies and blennies are usually great in small tanks. Two perculas would probably be fine in that set-up for a while also.