Black Emerald Crab

[PufferGuy]

Is it true that as emerald crabs age and mature they turn black??

I was at the LFS today and i told the guy to check if he had any emeralds left because i couldnt see any in their invert tank. He looked around and showed me this big mofo black crab, like almost the size of a silver dollar and said that it was an emerald that was just matured.

I think he was just trying to make a sale because ive never heard of any black emeralds... also, would an emerald that big be a threat to fish/other inverts? or do most emeralds stick to algae/detrius?

 

[Bifferwine]

Yeah, they come in all sorts of colors. I've seen dark red ones, blue ones, white ones, gray ones, black ones... The larger they get, the more of a risk they may be to fish. Usually if you keep them well-fed, it's not a problem. But I have heard of some turning to the dark side if they get hungry enough...

 

[PufferGuy]

thanks, i think i made a good decision passing that big guy... especially with my mandarin in the tank

 

[d2mini]

Aren't they called emerald crabs because they are oh, i don't know.... emerald color?

 

[Melosu58]

They are mithrax crabs and I like Biff have seen them many colors. Green, White, Black and red.

 

[sen5241b]

I picked up a red mithrax crab just yesterday. I didn't know the red ones existed until I saw it.

 

[OmegaOmega]

Is it true that as emerald crabs age and mature they turn black??

I was at the LFS today and i told the guy to check if he had any emeralds left because i couldnt see any in their invert tank. He looked around and showed me this big mofo black crab, like almost the size of a silver dollar and said that it was an emerald that was just matured.

I think he was just trying to make a sale because ive never heard of any black emeralds... also, would an emerald that big be a threat to fish/other inverts? or do most emeralds stick to algae/detrius?

I started out with six emeralds (very small) that quickly grew. The each would fight and eat each other and then I came down to two. One of them is incredibly large - actually, uncomfortably large; especially for a tank my size.

I see him constantly clawing or reaching out to the fish (who so far have been smarter) but he/she has tried to attack me as well when I'm in the tank. Anytime I see him moving near I normally scream and jump away from the tank - sometimes taking equipment or some peripheral item out with me.

When I use sinking tablet or frozen food and keep him fed he generally remains docile but I'm just holding on to him until I transfer to the bigger tank this month - otherwise I'd get rid of him.

I will say, the six, when they were small, did an amazing job keeping the rocks and coral clean - but it would be a second-thought purchase for anyone with a smaller/nano tank, IMO.