I went to the craft store and picked up a bag of shells for 2 bucks, all various sizes, i put them in and they stopped fighting over shells/killing each other for shells. Hope this helps. I beleive the store was Michaels Crafts.
50 Gallon Oceanic: 2 maxijet 1200's, 2 150 watt visitherm heaters, BakPak II Skimmer with PS & BT, Coralife Lunar 2X65 watt Power Compacts
Filtration: 50lbs LR
.com, 60lbs sand
Swimmers: 2 O. Clowns, Yellow Watchman, Firefish, Yellow Tang, Dottyback.
Clean-Up: Several snail & hermits, Skunk Cleaner, 2 Peps.
Corals: 2 zoo colonies, yellow polyps, star polyps