Pairing Gobiosoma multifasciatum?

[kmw]

I picked up a green banded goby over the past weekend. S/he looks great, eating like a pig. I considered getting two, but had no ideas how it would work out in my tank (28 gal), and the LFS worker said "Well, most people only get one. But we have had one or two people get two" - big help. If I were to pick another one up, would one switch sex, or are the sexes fixed? What if I ended up with two males or two females?

I've spent hours looking over at wetwebmedia, and can't find an answer using Google.

Well, I found this article: http://www.reefkeeping.com/issues/2002-09/hcs3/ in which the author says he's successfully kept several species together in one aquarium. Is this the exception or the norm?

Anybody? Thanks..