white crab?

[Trigs]

so i was chillin in my room the other night, and i had all my mh and actinics off and everything and i come in to turn them on and i see a white crab no bigger then a nickle eating off of my rocks and once the halide got to its full spectrum it vanished into the rocks? it was a nice white with a bit of black stripes i think? hard to explain. Any ideas?

[don.ald]

try this link it may help

http://www.melevsreef.com/id/
http://www.melevsreef.com/id/crabs.html