Id say negative on the CC lol. Rays are bottom dwellers and going to spend some time down there. Having sand will be much better for them, for a number of reasons. Id advise on getting another skimmer anyways and also finding a way that you could turn the wet/dry into a refugium. Rays need very well maintained water and the more you have for equipment the better off you'll be. My advise would be getting either the coralife skimmer or setting up a sump, if you have the option for overflow. Let the tank sit for a while and possibly using UV would help as well. I might also consider learning the ropes of ozone and use that in your water. Id also have to agree on the 300 or larger as well. the bigger the tank, the better off you'll be in housing SW rays, Its best advised to keep them in one place as long as you can so you don't cause stress problems, or injure yourself.