Good question. Read read read read read. Then do some more reading. My eyes were bloodshot from reading about rays and I still don;t have them. this was months ago. I read up on them every once in a while, usually daily, about breeding, common diseases, feeding, weening, tankmates, etc.
use the search feature on here read the stickys and get Freshwater Stingrays from Dr. Richard Ross.... also there are many great vendors on here who have top notch rays and will ship to your door.... if you do have them shipped airport is much better....
i agree with all said above...im about to get into the stingray game and im doing major research. you gotta know little things like having a sandy substrate.