Unknown “crab” in tank?

James_O

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I just got about 3lb of live rock from my LFS a few days ago, and I just saw a little crab hiding in one of the holes!

It’s a terrible picture, but it’s at night:
887EC219-2DAC-481C-923E-ADAE4B46C5C3.jpeg


It’s brown and is about the size of a small spider.

Any clue what it could be? I didn’t provide much information, but it’s all I’ve got. :/
 

MaxTremors

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Is this a pest or something I should be concerned about?
It could be, but it could also be benign. Try to get a better look at it, see if you can observe what it’s eating. I’ve had many different little crabs come in on live rock, I usually leave them unless they’re an obviously identifiable pest or I see them eating corals or other inverts.
 
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James_O

James_O

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It could be, but it could also be benign. Try to get a better look at it, see if you can observe what it’s eating. I’ve had many different little crabs come in on live rock, I usually leave them unless they’re an obviously identifiable pest or I see them eating corals or other inverts.
I honestly can’t tell you anything about it right now, because it has itself crammed in that hole, lol.

I’ll see if he comes out tomorrow. :)
 

Alexopora

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I think the crab may be a “coral crab” or a “gorilla crab”. Are either of these bad?
A coral crab normally comes with its host coral (e.g. acropora, pocillopora). There are two main types if I remembered correctly, Tetralia and Trapezia. They are generally smooth textures and smooth claws. Coral crab aka Acro crabs are good and beneficial.

Gorillas on the other hand, either catch it and throw, or if you are like me give it a new home in the sump. It does a pretty good job of keeping my filter media and crushed coral clean. Just make sure there is no way for the crab to re-enter the DT.
 
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James_O

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A coral crab normally comes with its host coral (e.g. acropora, pocillopora). There are two main types if I remembered correctly, Tetralia and Trapezia. They are generally smooth textures and smooth claws. Coral crab aka Acro crabs are good and beneficial.

Gorillas on the other hand, either catch it and throw, or if you are like me give a new home in the sump. It does a pretty good job of keeping my filter media and crushed coral clean. Just make sure there is no way for the crab to re-enter the DT.
Oh, this one has “hair” on its back/claws, which makes me think it may be a gorilla crab?

Also, I don’t have a sump, just a HOB.

Do they eat live coral or something? Or why are they generally bad?
 

Alexopora

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Oh, this one has “hair” on its back/claws, which makes me think it may be a gorilla crab?

Also, I don’t have a sump, just a HOB.

Do they eat live coral or something? Or why are they generally bad?
When it doubt, toss it. I have never personally seen its damage for mine was teeny but a lot of reefers have reported that it eats and picks on coral flesh. Sometimes bigger specimens might eat smaller fish.
 
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James_O

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When it doubt, toss it. I have never personally seen its damage for mine was teeny but a lot of reefers have reported that it eats and picks on coral flesh. Sometimes bigger specimens might eat smaller fish.
That’s to bad. I was so excited to see life in my tank. :(
 
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