I would suggest doing some research about brackish water and brackish species before you get a BB goby. There are lots of neat fish but many of them need very large tanks (including monos, scats, etc). I keep two violet gobies in my tank they get large and don't take !*#$ from any of my other fish (2 med archer, 1 columbian shark, 1 wide bar datinoid). but in a large enough tank I don't think it would be a problem to keep them with BB gobies (like say at least 40 much better 55gal+).
-Hutch