Maybe throw some more empty shells in your tank? I tossed a bunch in mine last night and this morning one of the crabs had switched shells.
Crack is probablly less addictive than saltwater aquariums
47G Bow, 45# Live Rock, DSB
, 10g Sump w/ LR
Rubble, AquaC Remora Pro, 2 Maxijet 900(s), Clean Up Crew - (7) Scarlet Hermits, (2) Emerald Crab, (11) Turbo Snails, (3) Nassarius Snails, (1) Fighting Conch, (1) Sand Sifting Star, (1) Skunk Cleaner Shrimp
* (2) Yellow Tail Damsel
* (2) Percula Clow