These are an awesome shell dweller! Be careful about getting these from people who just net a few fish from the tank -- the males guard the water column above the shells, so unless you're getting shells, a "random scoop" of fish will net you all males.

You're bidding on a whole bunch of these guys: at least one guaranteed pair, 4 shells, and a bunch of 1/2" fry. The pic shows the pair you will most likely get (and another pair in the background) along with their fry.