Is it normal

I was checking my tank after lights out and noticed some small crabs about 10-15mm across, These could only have come from the live rock.
Is it normal for live rock to have things like this in or should i be worried.

 

it is normal to have stowaways(called hitchhikers) some are good some are bad some are benign.

but it is important to take note of 2 main hitchhikers crabs/shrimp and anemones. these are the two most common bad ones. what your gonna want to do is id the crab. there a link floating around that has a bunch pictures of different ones, i will try to find it


note: not all crabs and anemones are bad

 

also next time you see him if you could catch it and take a pic we could help with the id

 

I found a dead one the other day, It's sealed up in the freezer. I'm due back at work in a little while so i will only get time to photograph it in the morning.

 

Back from work ;D Here are a couple of pics of it, The ones that i have seen in the tank seem to be a creamy pink colour.

 

Xanthidae Crabs ..not reef case

Go to link below then info links on left, then hitch hikers, then crabs

Chuck's Addiction

 

Done a search and it seems that Xanthidae Crabs are a family of crabs not an individual also in the family are the boxer crab and the arrow crab still not to sure. Do i need to remove them from the tank. If i do any tips on how to catch them as they only come out at night and shoot back inside the rock's after they have seen the tourch.

 

Yes you should remove them. There are some traps you can buy but have seen other forums where people have built there own.. I think Packleader has made his own out of 2 liter coke bottle.. I will look around and see if I can find it, you could also drop a message in his profile and see if he gets back to you.