I've had no crabs of any type in my tank for over a year now, and its all the better for it. Nassarius and brittle stars (not to mention bristle worms)are just as good of scavengers and they don't kill fish, eat corals, or decimate your sand bed fauna. But, to each his own. If anything, I'd say that is a few too many clean up critters, some will starve and you'll end up with less than that.
They who can give up essential liberty to obtain a little temporary safety, deserve neither liberty nor safety -- Benjamin Franklin