I don't see why you couldn't put a pair of the African Pipefish, Doryrhamphus excisus in there. They don't get very large. Just make sure you read up on them. They do eat prepared foods but are still a lil' touchy when it comes to their care. Even though they eat prepared foods most of the time, you want to make sure you have plenty of live foods for them as well. They are very peaceful and need to be kept with peaceful tankmates. Shouldn't be a problem in a tank that size as you can't really put many of the aggressive fish in there...lol.
