Emerald crab size - Reef safe when they get big?

[MegabiteOG]

I have 4 Emerald crabs in my mixed reef and curious if I should have any concern when they reach full size. I have a couple of them that are already pretty big. About 2" I'd say. I see them picking around some of the corals but don't think they are picking on the corals them self. Also, I see something that looks like aggression on occasion when a fish swims by them.

 

[fishywishy]

I’ve never had a problem with them. If they aren’t eating corals already they probably won’t in the future.

 

[MegabiteOG]

I’ve never had a problem with them. If they aren’t eating corals already they probably won’t in the future.

Thanks. Hopefully that continues being the case.

 

[mattroth54]

My big one seems harmless. He does swipe at fish occasionally when they swim by. It’s kind of funny.

 

[MegabiteOG]

My big one seems harmless. He does swipe at fish occasionally when they swim by. It’s kind of funny.

That's exactly what mine are doing. I was more concerned about this behavior at night when fish are tucked in.

 

[ColorMeGone]

I feed mine Nori strips that I cut up for them and my Pitho crabs. That way they don't starve to death or eat on my corals. They have made my tank spotless and so they need to eat. lol

 

[Cheezeits]

If you have a refugium you can just move them to there if they start to become a problem.

 

[BristleWormHater]

Every male emerald crab ive had has eaten my coral, havent had that problem with females, that could be a relevant factor.
I doubt they will be aggressive to healthy fish, they are just too slow, for the most part only swimming crabs are dangerous to fish. Crabs will put up their claws if they feel threatened, they are likely scared of the fish and preparing to defend themselves not being aggressive.

 

[MegabiteOG]

Thanks for the replies all! I agree with @BristleWormHater that what I'm seeing is likely a defensive move when fish swim by. I will keep an eye out on the coral. Mine also keep things super clean @ColorMeGone. They even clean my snails.

 

[BryanM]

I've never had a crab that didn't start nipping at softies. Sucks for me because they are neat.

 

[MegabiteOG]

I've never had a crab that didn't start nipping at softies. Sucks for me because they are neat.

So far I haven't witnessed any of it. Fingers crossed.

 

[mattroth54]

That's exactly what mine are doing. I was more concerned about this behavior at night when fish are tucked in.

He doesn’t seem like a hunter when the fish are sleeping. It’s only a friendly swipe during the day. He’s harmless.