D. diadema questions.

Been a while out of the hobby but I'm finally coming back with some D. diadema I am purchasing in 30 minutes or so. I am getting three and I had some quick questions. I know about housing and all. However I was wondering if these can be kept together? They are adults. I have three cages setup but I also have an empty MASSIVE cage and it would be cool to maybe get a communal going.
Thanks,
Nate

How massive is massive? These guys typically do well together if they have lots of places to hide and plenty of food. Cannibalism is pretty low in this species (I think Orin said in his book that he had 2 casualties over 2+ years...), so you shouldn't have to worry too much. Communal enclosures of amblys are awesome