HAHAHA! you got the exact opposite type of sand!!!!!! man it kills me because these people have much nicer rays and larger tanks than I and it kills me because most just see a ray in a lfs and are like "thats a cool looking fish i'll take 1 or 2. a week later after googling freshwater stingrays and finding this site their posts are " help my stingray won't eat, or my ray is curling" i try and help, but its hard not to laugh when someone buys the exact opposite of what is needed for rays! just go bare bottom and make it easier on yourself!!! now lemme get off my soapbox and answer your question
if its sand you want and want it cheap go to your local pool and spa joint and buy a bag of NON SILICA spa sand!