Gorilla Crab?

[wwarby]

I’ve just recently set up a quarantine tank with a couple of lumps of live rock, and today I noticed a clicking sound coming from the tank. Immediately I thought mantis shrimp because I know the sound well (I own a peacock mantis) and the clicking might well be a mantis or a pistol shrimp, but when I observed the tank for a few minutes after dark this little crab popped out of the rock. He’s about half an inch across, if that. When he emerged the clicking stopped- but surely something that small couldn’t make an audible clicking noise? It’s nowhere near as loud as my fully grown peacock whacking the her burrow (or the glass ) but it sounds like tapping a plastic pen against the glass.

Is this a baby gorilla crab? If not, what is it? And either way, could it be the source of the clicking or have I got another critter in that rock somewhere? And if it is a gorilla crab, should I try to remove it? I thought it was pretty cool finding a crab on my rock but word on the street is gorilla crabs are bad news.

 

[JGT]

Not likely it’s the crab. Most likely a pistol shrimp making the clicking sounds. Looks like it could be a gorilla. Pics of the claws could help confirm. Black claws is typically a gorilla.

 

[wwarby]

Not likely it’s the crab. Most likely a pistol shrimp making the clicking sounds. Looks like it could be a gorilla. Pics of the claws could help confirm. Black claws is typically a gorilla.

Cool, thanks. He’s disappeared back into the rock now but I’ll try to get a picture with the claws when I see him again.

I don’t mind getting a free pistol shrimp if that’s what the clicking turns out to be. It’s been suggested on a different forum site that I should put the rock in a bucket without water for a few minutes to see if whatever it is crawls out looking for water. Any issue with doing that? Id rather not start quarantining fish in the tank without knowing if it contains a predator lurking in the rock!

 

[JoJosReef]

If your rock has lots of coraline or any sponges on it, exposing to air will likely cause a die-off.

Would be good to see the claws on that one. It is darker than the gorillas I've gotten off of gulf live rock, which were more sand-colored with black pointy-tip claws. Those are definitely "straight to sump" hitchhikers. If you can get an accurate count of the legs (omitting claws) and you see only 3 on either side with 4th "leg-like" appendage that's usually tucked in, then it could be a porcelain, i.e. non-true, crab--but I think less likely.

safest bet is to sump it. I've got a gorilla living in the return pump chamber of a 10g AIO that's been surviving and growing for 9 months now.

 

[vetteguy53081]

Not sure of a pistol. Need pics under white lighting and gorilla will be hairy with Black Tips on its claws

 

[wwarby]

I think it's a red eyed reef crab. I'll keep an eye out for him and try to get better pictures to confirm. If so, I wonder if I should just leave him be for now? I'm going to be using this tank to quarantine fish - not sure yet what I'm going to do about corals, but it seems unlikely the crab will pose any threat to fish and I can decide later what to do if I start quarantining corals. If I caught him and moved him to the sump, would he get enough food? This is a 13 gallon Fluval Evo with a two inch square chamber under the weir that he could live in, but there's nothing in it except the heater.

As for the clicking noise, I remain convinced there's something else living in the rock - either a mantis or pistol shrimp probably. The rock does have some coraline algae (no sponges on this particular piece that I can see). I'll leave it submerged for now. The tank seems to be cycled so I was planning to get my first fish into quarantine soon. If it's a pistol shrimp then I'm happy for him to just stay there but if it's a mantis I don't want it predating my fish obviously.

I don't want to upset the water quality with unnecessary die off, but since I have nothing quarantining in the water at the moment, an extra week or so letting the rock absorb the ammonia from the die off won't hurt anything. Is there any better way to find out what's making the clicking noise?

 

[JoJosReef]

I have an Evo, and I don't think that would be a great place for a crab. In my IM Nuvo 10g, I have the gorilla crab that's been there since Jan (likely got came in hiding on a piece of rubble I put in the back for extra bio filtration). But that chamber actually has a lot of space in it since it runs the length of the bottom--just very dark.

Do you have a local reefing community? I've posted gorillas I pulled from my DT and usually someone is willing to put them in their larger sump/refugium.

Since this is just QT no reason not to take the rock out of water to shake the hikers out. Was thinking of DT rocks and they look so nice when they're still fully alive.

 

[wwarby]

I have an Evo, and I don't think that would be a great place for a crab. In my IM Nuvo 10g, I have the gorilla crab that's been there since Jan (likely got came in hiding on a piece of rubble I put in the back for extra bio filtration). But that chamber actually has a lot of space in it since it runs the length of the bottom--just very dark.

Do you have a local reefing community? I've posted gorillas I pulled from my DT and usually someone is willing to put them in their larger sump/refugium.

Since this is just QT no reason not to take the rock out of water to shake the hikers out. Was thinking of DT rocks and they look so nice when they're still fully alive.

Yeah I can probably find somebody locally who'd be willing to take it if necessary. It doesn't seem right putting it in a tiny empty section of the sump in my QT. I don't think I need to be in a desperate hurry to get rid of him though - I'm still new to this hobby and I quite like that I found a couple of living things in my rock (the others being a couple of asterina starfish and of course the phantom clicking animal that's in there somewhere). I'm not going to be keeping expensive or difficult corals - I haven't bought any yet but initially it'll be easy softies only, so the crab might not be any threat to them. If I get rid of any hitchhikers I want to make sure I'm doing it for a good reason.

 

[wwarby]

I managed to get the crab out of the rock today. I took the rock out of the water and inspected it with a torch where I found him tucked in a crevice, and coaxed him out with some tweezers. I've put him in a bucket for now - I figure I shouldn't leave him in the quarantine tank because he'll be harmed if I need to treat with copper, and I don't have any tanks with a sump that I'd feel right about dumping him into. My LFS has advised against putting him in the display tank, so I'll see if anyone in the local reefing community wants him otherwise he may have to end up becoming a snack for my mantis shrimp. Pretty sure I've got a pistol shrimp in the same piece of rock but I've not seen it and I'm not going to break the rock up looking for it so there's not much I can do about that for now.

I think this is a red eye reef crab. Any advances on that?

 

[firechild]

I couldn't tell you what exactly that one is but as a general rule, crabs with pointy claws should be evicted, crabs with flat tipped claws are useful. There are exceptions, such as symbiotic crabs that live in SPS and a few other corals, pom pom crabs and some anomurans (such as porcellain crabs) which are not true crabs - though this group also includes hermits crabs which are arguably not reef safe either.

 

[JoJosReef]

Crab hitchhiker ID Please

Found this very nocturnal little guy searching with a red flashlight after lights out. It's shell is about the size of a quarter. I found his cave and when it's time to stay inside, it makes a wall/door with live rock rubble to lock himself in. Just wondering what this little Indonesian buddy of ...

www.nano-reef.com

This looks like a crab you don't want anywhere near your display. Someone's sump, or feed to mantis, I would say. Quick google on these pulls up a bunch of hits for "aggressive crab".

 

[wwarby]

Crab hitchhiker ID Please

Found this very nocturnal little guy searching with a red flashlight after lights out. It's shell is about the size of a quarter. I found his cave and when it's time to stay inside, it makes a wall/door with live rock rubble to lock himself in. Just wondering what this little Indonesian buddy of ...

www.nano-reef.com

This looks like a crab you don't want anywhere near your display. Someone's sump, or feed to mantis, I would say. Quick google on these pulls up a bunch of hits for "aggressive crab".

Yeah I'd also found that thread on nano reef - definitely looks the same. I took him outside for a photo in better light. I kinda like him, but definitely agree I don't want him in a display tank after what I've read. Decided I'm not going to put him in with the mantis on second thoughts - there's too much risk the mantis will turn her nose up at it and the crab will scuttle off into the rock where I'll never be able to get him out again, so plan A is to try to offload him to somebody local. If that doesn't work I'll ask if the LFS will take him back. I don't want to kill it really so fingers crossed I won't have to resort to that.

 

[wwarby]

Sadly I had to euthanise this crab. The LFS didn't want it back (for understandable reasons) and I tried unsuccessfully for several days to find a local reefer willing to take it, even offering to drive or pay for postage to offload it but got no takers. Not where I wanted to end up, but I didn't see any other viable options - they are by all accounts menaces to reef tanks and I couldn't take the risk of keeping it. I went with the shoe method of dispatching it, following advice from more experienced reefers in the UK - it was that or the freezer, but the shoe seemed kinder as death would at least be immediate. Poor thing - hope I don't have to do that too often in this hobby.