What type of crab

[Robinski]

This crab has been in my 2nd hand tank since I got it a month ago. Seen it a few times but it hid in the live rock well.

Found it this morning with its carapace open. There doesn't seem to be any "meat" or "guts" in it. I think it might b a molt. Can the molt whole like this?

What type of crab? Black claws make me think it is bad.

 

[vetteguy53081]

Member of mithrax group. Black claws are a no no - remove

 

[Tired]

That's a molt, yes. This is how crustaceans molt- they pop the carapace up like a lid and drag their whole body out.

That looks like maybe a stone crab. They can be neat in a sump, and that one at that size is going to be relatively safe for awhile, but you don't want that sticking round long-term.

If you don't have anywhere to put it, kill it humanely. Crustaceans are thought to feel pain, so should be humanely euthanized when needed. Either crush it swiftly in one clean motion, or euthanize it with clove oil.

 

[WVNed]

There are a million types of crabs. Some grow quickly and some dont get much bigger than the one in your pic. I put mine in my sump and still have them. They are not small and cute anymore.

Generally a molt will look like an intact animal except the eyes will be clear and empty like no one is home.
Because they arent.

 

[Tired]

Oh, you can keep that molt, by the way. If you take it and pose it nicely, it'll dry out and set in that position, and will be a neat little specimen that won't rot or anything. You can use a pin to nudge the eyes and antennae into natural positions, and even look up "insect pinning" for reference on how to position and hold the legs, if you want to try for a really natural pose.

Thick, black-tipped claws mean that's a crab that will grow to a decent size and be potentially threatening to livestock. They can be cool sump inhabitants, and are easy to care for (just chuck meaty food in a few times a week), but shouldn't go in the main tank.

 

[Robinski]

I'm going to struggle to get him out seeing that the rock is full of gaps and I only see a pincer at night, never during the day and have never seen the whole crab.

 

[Tired]

Bottle trap is probably your best bet, or a tilted, baited shot glass. Or go at night with forceps and a red light flashlight, place food juuust out of his reach near the rock, wait for him to come out, and grab him.