I had a 25-inch iridescent shark (I rescued him 11 years ago) in a 1000 gallon pool with 2 castexi, 1 leo, 2 motoros. They'd been together 18 months. Recently I came home one afternoon to find the ID shark dead with a puncture that was in under one gill and out above an eye. Dead as a doornail and the sheath was missing from the leo's barb, so I assume he did the deed. Made me very sad but there's always that risk when you have tankmates in with rays.