Reef safe"ish"...until they're not. It's like when someone asks me if my pet (dog, bird,snake...) will bite. It certainly CAN but in the right circumstances and based on past experiences it is highly unlikely. Just remember it's there if anything looks wrong. It's probably been in there for a long time and this is the 1st time you saw it. I don't see mine often and when I do it's usually early or late.