There are two distinct species of BB gobies out there in the stores. One is Brachygobius xanthozona (8 rays in dorsal fin) and is a brackish species but can live in freshwater. They have unbroken black stripes. The other species is Brachygobius nunus and they do not tolerate fresh water.
copied from http://www.ultimatebettas.com/index.php?showtopic=196
hth
you need a feature fish , say something like a large(ish) Ornate Bichir i think that would make the tank really special , I might just know a man who has one and dont want much for him