you could have around three in a 55 gal and from what i have heard as long as there is enough food, they do great in groups. i think a 20 is the miniumum for a bandensis, but i think around a 30 is prefered.
if you live by the coast your fine, you can just feed them local crabs/shrimp and such, if you are like me and inland, you will have to buy the food, i buy 20 vulgaris shrimp every two weeks, and its like 18bux. so thats not that bad $9 a week. i buy it from the aquaculture store.
FWICT, we only have a few data points supporting this and not supporting this, so it may be premature to state it as truth (not that that is what you are doing! )
Also important to note, that they seem only to have done well in groups (in the groups they have done well in) if they were raised together. S. bandensis that are wild caught seem to fight a great deal if kept together.
thats very interesting, i wonder if they realize that they are related? but your the closest thing the an expert righty so you obiviously know more then i do. If they are infact raised together, dont they seem to react well. from all the stuff i have been reading, as long as there is plenty of room and food, they seem to do well. although i would assume that there would be some fighting( one of mikeys posts as well as your site)
btw they lil guy you sent me is doin great, and getting big.