Crab sighting - Is he a danger to my tank?

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Pinkasylum

Premium Member
[I was looking at my tank just now and I saw a very ugly looking crab. I did some research on Reefcentral and saw many posts describing the same kind of crab, but none IDed it or said whether it posed any danger.

It is probably about the size of a dime, with black and white striped hairy legs. His body and claws are brownish with white bumps.

He has been hanging out on a piece of spiny figi that was covered with some type of hair algae. There used to be little red and white striped feather dusters all over the rock that came out of white tubes, but I haven't seen the actual feather dusters come out in quite some time. Did he eat them all?

Any ideas? Is he a threat to my tank?

Thanks!]



Edited By Pinkasylum on 1080943878
 
[Bad, Bad, Bad!!! I hate rock crabs after killing 6 I bought a zebra eel with a health liking of them kill it now!!!!

Rock crab is their nick name the hairy legs act like algae to unsuspecting snails then they sink their claws into the shell and rip him out quite brutal.]
 
[agreed. these bad crabs will also sneak up on sleeping fish....
One LFS owner told me the general rule of thumb is that crabs with one claw bigger than the other and claws of brown & white, or red & white are the bad ones. You'll have to build or setup a crab trap to catch it.]
 
[I boiled the live rock in fresh tap water. it ran out and then melted months later several sponges went all over the rock work]
 
[okay, well I looked into my tank today to see if the crab was still in the same rock, and let it suffice to say that parts of him were...

all that is left is a claw and a few legs. Any ideas as to what dismembered him?

Perhaps it was the same pest that killed my yellow tang?]
 
[Had somewhat the same experience with an emerald green - 'cepting he started looking a mottled bleached-out white and green and then it seems like the next day or he/she/it had been reduced to component parts...have to assume it was the dreaded bristleworms and/or hermit crabs
Did you know that bristleworms can grow to as much as 13 1/2 ft long in a 5" dsb?
Me, neither, just made it up though so it must be true...]
 
[Melissa, you may be looking at a molt.]
 
[I was thinking the same thing. If it is a molt he may be hiding extra good for a day or so till his new shell hardens.]
 
[I think terry and marc are right though I never saw my rock crab molt... p.s. they run sideways very fast. And the traps the backwards small coke bottle doesn't work that well. they seem to be too smart for it. Generally not leaving the rock work.

Zebra eels are worth it :tongue:]
 
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