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.

Here is my photo.

[Ninong]

With very few exceptions, most true crabs are opportunistic omnivores. I think it's safer to remove them if you can.

[Firefish]

This little fella hitched in on some uncured lr I bought a while back. I found him one day and figured the trigger would love a little snack since he was only the size of my thumb nail, so I forgot all about him. Big mistake...
After a couple months, I noticed there weren't as many fish in the tank, I was two fish short. I looked all over the place for them. After a couple of weeks later and still not seeing my lost fish... I saw "him" again! This time a whole lot plumper and meaner looking. It took me forever to catch him, they're quick little bastards!
I finally had to remove the rock he was residing in and put it in the sump until he came out to play, then I removed the rock, caught him and brought it to the lfs.

I'd get him out asap, or buy a big trigger

[Ninong]

I'd get him out asap, or buy a big trigger

...or a big octopus!

:eek3: