i think when it comes to rays, knowing whether or not the ray is healthy before buying is very important. I'm sure you've heard of the death curl, which apparently almost always results in the ray dying.. check the ray's stinger as well, you need to treat with meds/antibiotics if you notice any injury, as the fleshy sheath that surrounds the stinger is usually affected (torn off, cut, etc etc - it doesn't grow back either) during the ray's capture and transportation... usual practice is to place a piece of airline tubing over the stinger - you need to get this removed once you bring your new ray back home.
All the best with your new rays!
All the best with your new rays!