Crab ID

[Daenion]

This fella came with live rock and was living under it. However, for the past month or so it has been roaming around during day time and got pretty big.

Might be gorilla crab but I really don’t know. Catching him was surprisingly easy.

 

[Cthulukelele]

That's a ruby mithrax crab. It is functionally the same as an emerald crab with the same caveats. Usually a helpful herbivore but the big ones can go rogue occasionally eating coral/small critters and the females are usually nicer than the males. Since you have it out and can check the abdomen that's the easiest way to tell the males from the females. Pic attached

 

[Daenion]

That's a ruby mithrax crab. It is functionally the same as an emerald crab with the same caveats. Usually a helpful herbivore but the big ones can go rogue occasionally eating coral/small critters and the females are usually nicer than the males. Since you have it out and can check the abdomen that's the easiest way to tell the males from the females. Pic attached

Thank you very much. It is a male. Would it bother BTA?

 

[Cthulukelele]

Thank you very much. It is a male. Would it bother BTA?

For a BTA I'd say probably not. They tend to prefer the tastiest of the soft coral and fleshy lps. If you have any super small fish could maybe go rogue, but asl long as there's plenty of algae and if it gets MASSIVE you consider removing it I don't imagine you'd have much issue, but I'm partially team you can never fully trust a crab.

Ultimately it's up to you. They're interesting creatures that can be mildly beneficial in the tank but do come with some low-medium risk in the very long term for small fish and certain coral

 

[Cthulukelele]

I'd probably keep it because I'm a sucker for a hitchhiker and I'd take the small gamble

 

[JoJosReef]

Thank you very much. It is a male. Would it bother BTA?

Doubtful. I've never seen an emerald touch a BTA. I have seen them with torch polyps in their mouth and picking on zoas or other corals. That's usually an immediate dismissal, although at that point they're usually not doing their job anyway.

 

[Daenion]

I'd probably keep it because I'm a sucker for a hitchhiker and I'd take the small gamble

I got a refugium in the sump of my main tank. He is going there.

 

[Cthulukelele]

I got a refugium in the sump of my main tank. He is going there.

That crab is about to be in heaven

 

[Daenion]

That crab is about to be in heaven

I presumed he would enjoy that place.