Acro Crab , Need ID please!

[Rohirrimus]

Hello reefers,
I got this frag that came with the crab. The crab was already on the coral in LFS and frag looked great so I figured it’s reef safe.

But in couple of days part of went from this:

To this:

If you look at the circled part it’s clear that something is eating the polyps.
Do you think that coral can recover from this or should I cut off that branch?

here are some more pictures of the crab, hopefully someone can tell me if the crab is bad or is there something else eating my coral:

For now I removed him from the coral and placed him in a breeder box. If identified as bad I’ll chuck him into the sea.

thank you in advance

 

[WheatToast]

I am not a coral expert, but the crab appears to be a gorilla crab (Xanthidae sp.). These are not reef safe, though one might make for a unique addition to an empty part of a sump if you have one. Please do not introduce any aquarium organisms into the wild, even if they are native species, as they might have picked up nonnative pathogens in captivity.

 

[Reefing102]

I agree. Looks like an xanthid. Usually the good Acro crabs are smooth not hairy

 

[A Young Reefer]

Looks like a furry coral crab (Cymo melanodactylus) I would consider them good for the most part.
Check this out it might help:

Guide to Common Hitchhikers in reef tanks.

The purpose of this thread is to hopefully assist hobbyists in obtaining the correct id and method of treatment to common hitchhikers. Both; the good ones and the bad ones. 1) Anemones: Some times called the flowers of the sea, many hobbyists keep them intentionally for their striking colors...

www.reef2reef.com

Edit: there are always risks involved with coral crabs imo the cymo melanodactylus doesn’t grow as large as the other species in the family Xanthidae and tends to rarely pick on fish if never in my experience. If it was in my tank I would remove it or rehome it if that was an option, avoiding any risks.

 

[Rohirrimus]

Looks like a furry coral crab (Cymo melanodactylus) I would consider them good for the most part.
Check this out it might help:

Guide to Common Hitchhikers in reef tanks.

The purpose of this thread is to hopefully assist hobbyists in obtaining the correct id and method of treatment to common hitchhikers. Both; the good ones and the bad ones. 1) Anemones: Some times called the flowers of the sea, many hobbyists keep them intentionally for their striking colors...

www.reef2reef.com

Edit: there are always risks involved with coral crabs imo the cymo melanodactylus doesn’t grow as large as the other species in the family Xanthidae and tends to rarely pick on fish if never in my experience. If it was in my tank I would remove it or rehome it if that was an option, avoiding any risks.

Thanks for the answer,
I think you are right,
I was reading this yesterday:
https://www.reef2reef.com/threads/crab-eating-acropora.158139/
And that seems to be it. From what I read people seem to like them in large colonies as they nip on a coral here and there.

I think that’s my issue , that the frag is just too small so the tiny amount of polyp eating is causing is killing my frag . Also the person where I got the coral from (coral growing expert) saw him but didn’t mark him as bad.

do you think there could be some other reason my acro lost its polyps or is it definitely the crab ? Thanks

 

[Rohirrimus]

I am not a coral expert, but the crab appears to be a gorilla crab (Xanthidae sp.). These are not reef safe, though one might make for a unique addition to an empty part of a sump if you have one. Please do not introduce any aquarium organisms into the wild, even if they are native species, as they might have picked up nonnative pathogens in captivity.

Thank you, it was my first thought too but the gorilla crab doesn’t match.
the head and claw shape are a bit different. Seems to be furry coral crab like the other comment suggested

 

[A Young Reefer]

Thanks for the answer,
I think you are right,
I was reading this yesterday:
https://www.reef2reef.com/threads/crab-eating-acropora.158139/
And that seems to be it. From what I read people seem to like them in large colonies as they nip on a coral here and there.

I think that’s my issue , that the frag is just too small so the tiny amount of polyp eating is causing is killing my frag . Also the person where I got the coral from (coral growing expert) saw him but didn’t mark him as bad.

do you think there could be some other reason my acro lost its polyps or is it definitely the crab ? Thanks

I can still see polyps here and there, however it is most likely that the crab is picking on the polyps and irritating it.
is this the original Color of this acro? It looks a bit browned out.

 

[Reefer Matt]

That crab is eating the acropora. Gorilla crab. I had them too. Reef safe acropora crabs have a smooth shell and bright colors.
Thread 'Crab eating Acropora?!' https://www.reef2reef.com/threads/crab-eating-acropora.158139/

 

[Rohirrimus]

I can still see polyps here and there, however it is most likely that the crab is picking on the polyps and irritating it.
is this the original Color of this acro? It looks a bit browned out.

It's still new, got it last week, and it got a bit agitated in transport since above it there was a hammer floating stuck to the styrofoam, but got free and probably hurt it a bit.


But what I am referring to is this circled part I showed above, clearly it looks like it was eaten

 

[Tonycass12]

Get rid of that crab if you haven't already. I wouldn't go trimming the coral just yet, if you tank is stable and the parameters are right it will heal quick. If you notice algae growth on the damaged spots then I would give it a trim. I have multiple maricultured colonies and almost all of them came with one or more acro crabs and the occasional gorilla. Just pull em as soon as you see a hard crab and kill it!

Gorilla crab from my colonies

Acro crabs that live in almost all my larger colonies. I have yet to see a brown one they tend to be orange, orange and white or black and white with very smooth exterior almost like porcelain.

 

[Rohirrimus]

Get rid of that crab if you haven't already. I wouldn't go trimming the coral just yet, if you tank is stable and the parameters are right it will heal quick. If you notice algae growth on the damaged spots then I would give it a trim. I have multiple maricultured colonies and almost all of them came with one or more acro crabs and the occasional gorilla. Just pull em as soon as you see a hard crab and kill it!

Gorilla crab from my colonies

Acro crabs that live in almost all my larger colonies. I have yet to see a brown one they tend to be orange, orange and white or black and white with very smooth exterior almost like porcelain.

Thanks,
I think it is a higher chance that it's that furry coral crab, but I returned him to the LFS yesterday ( and ended up getting more Acropora ) . It seems like very soon when these colonies grow I'll have to get a bigger tank