Saw pics of your tank. Depends on the agression of the current fish, but many people keep rays with your fish. Not sure on the aragonite sand someone else will have to chime in there. Is aragonite crushed coral? If so, there may be sharp edges. Also I read that you were using it to buffer the ph in your tank. Just have to watch the ph as rays can be sensitive to ph change. I would think 6-8" ray would do fine with those tankmates as long as they are still small. If you have a way to keep him in a quarentine tank to get him eating and put some weight on him, it would be ideal. The stress of shipping and throwing him in with other fish right away may be too much so quarentine is best. When you do put em together, keep an eye on em, or put in a divider for a little while. Should make an awsome set up. Good luck.
