ok - this all makes more sense - they play one role, then the other.
As the eggs first appear as unfertilized (clear) - and turn green when fertilized, it would be LOGICAL that they first play the role of female, produce eggs, and then turn male and produce sperm to fertilize, but the other scenario is that they are first male, produce sperm, store and then become female and use the stored sperm to fertilize their eggs.
I have observed that the females with eggs are very wary of each other, and make serious efforts to avoid each other (except during feeding when they only care about the crab/shrimp bites in the tank) - and that the one we have that is without eggs seems to be playing the role of suitor... but this could (and probably is) a misinterpretation of the behaviour.
However - there has to be some kind of cross-fertilizatin possibility, or the whole system leads into a downward spiral of bad genes - in-breeding of dogs ought to be the first clue that without diversity in genetics, their only lie problems down the road.
While I think that self fertilization through hermaphroditic behaviour is a way to continue the species, it's exclusive use can't be the only way to reproduce - could it?