Unknown Hitchiker

[marcingo]

It's hard to tell but I would say if its legs were stretched maybe an inch and a quarter.

Also I noticed another critter I havent gotten a really good look at it because it hides in my rocks in the dark but what it looks like is sort of like a hermit crab at least the arms and legs but it seems to live in the rock and its always kind of hanging from inside of the rock with its feet in the air. Crappy description I know.

Also the brittle sea star will it grow too big for my tank and is it a predator?