Got an arrow crab Friday and he has been an absolute rock star...so much fun to watch. I'm puzzled though, I read descriptions about him "after" I brought him home and they all list them as being carnivores. Since he's been in my tank he has done nothing but graze like crazy on algae and stuff in the sand...seen him also picking at life on the rocks (plant life) and jamming it in his grill. Last week I received my shipment of 25lbs of Tampa Bay Saltwater live rock and I am just amazed...and my son is 10x more amazed than I am. He has found some cup corals on one rock and discovered all these "spaghetti" worms that come out at night . We have two types of anenome (one which I think is the type I need to remove)...and last night I saw what I have found out is a "porcelin" crab (just slightly smaller than the size of my thumbnail)...there was another that was even a bit smaller that was a whitish (he scurried away too fast for me to really identify him) Have some turbos snails in the tank and they are doing an awesome job of grazing some of the algae that built up during the cycling of the tank.