Theres a Crab Living In My Live Rock - Good or Bad?

[Rollos]

Firstly hello, Newbie Member!

We've recently set up a new marine tank and are currently 'cycling' it.

We have 4 chunks of live rock in the tank and noticed a small crab popping in and out of a hole in the rock.

He's quite sweet, he does occasionally get brave and venture out but as soon as we look at him he runs back into his hole. Awww.

Anyway, my question is, should I crush him?

[blue_eyes53813]

If he isnt bothering anything I would just let him alone... Do you have a sump or refugium to put him in if he starts to bother things,? Dont crush him...

[addey]

whats the crab look like,i have had nothing but trouble with hitchickers and dont let the size fool you i have just captured the dark destroyer and he is only an inch across and he has been on a three month seek and destroy mission he has taken out 2 anemones 6"dia +1@8"dia my duncan witch he actually picked up turned around and shoved into a hole were he ate it.he is very dark on the body with brown/white legs and each claw is aprox the length of his body(thin looking pincers) i think he is a black mithrax apparently they arent to bad if you have the right food in the tank wouldnt risk it though,trust me it will break your heart

[Rollos]

No he's not bothering anything at all, but there's nothing to bother at the moment. It's just I read that if you see a little crab living in your live rock you should crush it?

[addey]

dont no if i have sent you a message about your crab as i cant use computers,breifly ive just caught the dark destroyer he has been on a 3 month seek and destroy mission he has taken out 3 anemones my duncan and vairous other stuff and he is only 1"across dont risk it,it will only lead to heartache he is dark on his body with slightly lighter legs with thin claws each as long as his body is wide DEADLY!!

[BigJay]

No he's not bothering anything at all, but there's nothing to bother at the moment. It's just I read that if you see a little crab living in your live rock you should crush it?

absolutely not. Most hitchhikers are generally good for the tank. There are the occasional bad guys. But bad is relative. Usually most bad hitchikers serve a very important role if used properly. Ie put him in a fuge where he can't pester your live stock and he'll probably help keep your fuge clean. Never kill anything , especially if your not sure what it is.
If you do not have a fuge a good technique is to use a small tank even a large tupperware will do. Put the rock in it with tank water and an airstone and try to lure him from the rock(ie put food on one side of the tupperware and the rock on the other). Then take a picture of it or put the rock back in your tank and take the crab to your local LFS for ID or donate it to them.
At this point since you have nothing to pester I'd just leave him where he is until the point comes you can snap a pic.

[lcstorc]

Don't squash him unless absolutely necessary. I would however remove him from the reef and put him in a sump or fuge. If he is hairy or has black tips on his claws he is likely a "bad" hitchiker and should be removed.

[Rollos]

At the moment I like him, he's the only movement in my tank, I've been staring at him all day. I really truely don't want to crush him.

He is a little hairy and he does have black tips.. Oooh dear.. But for now he can stay (can't he??)

[Rollos]

At the moment I like him, he's the only movement in my tank, I've been staring at him all day. I really truely don't want to crush him.

He is a little hairy and he does have black tips..

[BigJay]

If the very tips of the claws are black its a bad sign that it may be a gorilla crab. If the very tips are white then its most likely an algae eater/scavenger. Unfortunatly if it is a gorilla its one of those hitchhikers that should be isolated from your tank inhabitants. But they are a great fuge critter helping keep it clean.

[Rollos]

Yep, this is exactly what he looks like, he's picking at the rock, he seems really hungry!

[slakker]

I've lost a Pearly Headed, Kole and a Neon Dottyback... very likely to a hitchhiker crab... catch him and put it in your sump, it's not worth it. Crabs in general are "EVIL"!

[smarsh97]

Okay, since I have caught a ton of those nice "eh hm" Gorilla crabs from my rock, I will tell you how I do it. They are very smart little crabs. Crab traps won't work. I got a really long pair of forceps. I dump food in the tank and hide. When they come out, snatch them up and throw them in the sump.

Unforunately none of mine have lived very long in my sump. I don't know why. But it is what it is.

I am sure they ate my Tiger Goby as he lives in rocks as well.

Sandy

[lcstorc]

If you don't have any livestock then you could leave him for now if you like. You will want to remove him before you add your livestock since he will very likely be a threat.

[Rollos]

Thanks very much for all the advice, we're going to remove him today.

We don't have a sump so could I take him back to my LFS?