Crab from Live Rock Danger?

[Leonard]

After i put 5 live rock, there is a 5 crab in it. Black, red and white. No hermit crab. Is danger or not to let the crabs in my tank?

Please help me.

[leebca]

We'd like to help. But in order to help you we have to identify the crab. A description is not good. Can you post a photo of it?

[Leonard]

Here is my photo.

[leebca]

This photo doesn't do me much good for identification.

Has there been any indication of it harming fishes or other invertebrates? It seems 'well armed' for defense and attack. Hopefully its claws are more for mating. ;)

Now that you have a photo, I suggest posting the photo in the Reef Aquariums Forum here on Reefland.

[vaporize]

in general, crabs are opportunistic feeders, that is they will eat anything they can grab a hold of. So it becomes kinda a common practise to remove any crabs especially if you are going to have a reef tank.

Btw, just see that you are in Bali Indonesia, how is that treating you ;)

[Leonard]

i still dont have any clue. Some of my fish die, but i dont know attacked by whom. I thought crab only eat dead fish...

[leebca]

Crabs can be very aggressive. Some specialize in vegetation or flesh, but most, as vaporize pointed out, are omnivores and very opportunistic. They will eat whatever they can get their claws on. This includes the dead things as well as living things. Some sneak up on sleeping fish and 'catch' them. Some will kill and eat snails, and other crabs. It depends upon how hungry they are and the kind of crab they are.

In general if crabs are something you'd like to keep, then it is best to keep them alone.

[Clydelyle]

Here is my photo.

Judging by the wrinkly carapace it looks like some type of xanthid crab. Generally they are supposed to have some type of symbiotic relationship with corals defending them from predators, downside is they eat corals themselves. I've had several hitch in on rock I've harvested myself, amazing variety, don't think I've ever seen two that were the same. I'd get rid of it.

[weez1959]

I think I see some small flat plates on the ends of the claws, am I right?, if so these are usually used to pick at stuff rather than kill, I could be wrong...
He is cute though