are crabs nocturnal?

[shoura]

I am just setting up my first tank and got a mithrax crab yesterday--he started attacking the algae immediately then disappeared after a couple of hours--I saw him again after lights out but this morning he is nowhere to be seen. Do they only come out at night?

[dc]

Not always, I used to see mine during the day all the time. They do tend to hide a lot tho.

[Sk8r]

THey're pretty cryptic ---hide at the first sign of movement from you. The only reason he didn't hide at first was that he hadn't established a bolthole.