Since there is no Primer thread for this species yet, I have to ask. I've never had one before and it was recommended to me as a 'method' to help deal with Valonia algae. I do know their spines are venomous but not much else. Is there any species they don't get along with? Any special requirements? Aggressiveness in general? What are the more coveted (unusual or beautiful) species? Tank minimum size? Any info would be welcome. Thanks in advance.