Fuzzy, white crab?

[Ryan Friman]

I thought it was a sponge until I touched it and it moved. My girlfriend and I were joking it was a baby decorator crab since we have one in there, and it is white like him. anyways, what is in the picture?

 

[Ranjib]

Teddy bear crab probably. They are common in acropora. Not necessarily a pest (help in killing bugs etc), but they can be a nuisance, as they get big. Most people will get rid of them

 

[KJ]

Polidectus cupulifer (Teddy bear crab ) or Lybia caestifera (Decorator crab ) . Better picture help ID this crab