Magnificent! I was telling someone about Mantis shrimp. How big of a tank do they need to be in? I have that 6 gallon sitting around with just live rock and some snails in it. Would that size work?
So what is the smallest you can go? I have some interest. Read as little as 10 don't believe.
IMO, I wouldn't put them in less than 30G, preferable acrylic.