View Full Version : Id crab please

01/09/2016, 07:50 AM
Ok so please bear with me on this but I have not gotten a good look at the crab let alone a picture. It looks like a black mithrax crab. I don't remember seeing red eyes, and didn't notice the claw shapes. This morning I saw it under a rock either sifting through the sand or pushing the sand away from the rock. I have never seen an emerald so that before. How Concerned should I be about this? General id on crab from behavior? Thanks for your help.

01/10/2016, 01:38 AM

01/10/2016, 05:15 AM
Without a picture, there is no way to ID this. I would be concerned if any crab were in my tank accept scarlet legged hermits. I've had Emerald crabs grab fish while sleeping and eat them. So if it were mine it would be in the sump until I could get a picture for proper ID

01/10/2016, 04:23 PM
Having spent well over a week trying to get a Picture of my hitch hiking crab, this is best I can get. It has survived a dosing of ammonia, has avoided my traps for the last 4 nights..

Anyone have an idea what it might be? I'm going to sump it when/if I can catch it, unless someone tells me it's harmless (but unlikely from what I've been reading).

01/10/2016, 04:50 PM
Like I said before, the only safe crab IME is a Scarlet legged hermit and the only crab of any kind allowed in my DT. I got tired of my blue legged hermits killing each other and killing snails, they're in the sump along with my huge emerald crab.

I honestly don't know what kind of crab this is.

01/10/2016, 08:23 PM
Better than the one I have. This is the best I can get and got it tonight

01/10/2016, 08:24 PM
Looked like he was scraping something of the top of that rock but as soon as I moved he would duck back in

01/11/2016, 10:49 PM
Got mine. Oh the satisfaction. Took 6 nights but this morning, in the jar and not happy about it.

01/14/2016, 05:40 AM
Ok so last night I set up a crab trap and I caught the crab. So what is it...how safe...and good for sump or kill it?

01/14/2016, 05:41 AM
Another one

01/14/2016, 05:57 AM
From the front

01/14/2016, 06:28 AM
Yep, either kill it or sump it. I could be one of several different types of crab. I'm not positive on which it is, but you can tell from the claws it's not a good one to keep unless you sump it

01/14/2016, 06:32 AM
What I was afraid of. I have nothing in sump now, but it won't eat pods or nothing like that in the fuge? Also as a learning experience for me...what about the claws says it's not a good one?

01/14/2016, 07:24 AM
Nope won't eat pods Big chunky claws! But even that can be misleading on the ones with wimpy claws, like the arrow crab :hammer:

01/14/2016, 08:03 AM
But don't those claws look like a normal emerald crab claw? Or am I still missing something?

01/14/2016, 08:13 AM
You can see that the claws are large compared to the body size and that they are more pointed than rounded. That means that it is a predator and will kill for food. It might eat corals, or inverts, or even fish. Don't know and don't want to find out.

01/14/2016, 08:30 AM
Lyman - There are a lot of people with more knowledge than I, but I have a red mithrax crab in my DT. He's a great shade of red, fairly large and just walks around eating algae. I really like him.

This is not mine, but you can see that the claws are flat at the end. That's what it uses to grab and eat the algae. Anyway, that's one way to tell.


And how did you set up your trap? Do you have a photo?

01/14/2016, 08:58 AM
No photo of the trap, it was just a mason jar with a hunk of seafood in the bottom that I leaned against a rock. I set it up yesterday and this morning he was in the bottom of the jar.

I do see the flat spot in the photo. And mine is now living in the fuge so I'll see what he grows into. I love the grey bands on his legs though. Cool looking crab. Can't take the chance of him hunting anything in the tank though without a positive I'd on him. Looks like he is grabbing algae in the fuge though.

01/14/2016, 10:18 AM
I've got news for anyone with a mithrax crab green for sure and maybe red ones, they can and will catch small fish while they're sleeping and kill them.

I say it all of the time, the ONLY crab allowed in my DT is a scarlet legged hermit.

01/14/2016, 01:42 PM
Never had an issue with a Mithrax crab. I think there may be bad apples out there, but for the most part I've never even seen one look at a fish, other than in self defense. The flat claws on that guy makes me think Mithrax variety and a really cool one at that. I would leave him in my tank until he does something bad. Always keep an eye on everything.