Thanks doug,
dougefresh knows his bichirs better than I do, but I know brack. If I were you I would not get a scat or a mono in such a small tank. I here monos can be pretty aggresive and Figure 8s are evil little monsters when they are in small places. You could go with an archer because they grow pretty slowly and only get 8 inches where scats get double that. Also, a lot of killies make great brackishi fish. If you can get them, get some. Here are a few pics of my killies. Also, hogchokers only get 4 inches max and would be good for a 30 gallon. Wait on the monos and scats for now even though they are pretty fish.
Pipefish and brackish hermits just as a teaser. No hermits with puffers.