I've seen people say it's ok and others have said it's not, that it's too sharp. I have it in my 300 with my Giraffe cat and he constantly sifts it through his gills with no issues and no abrasions. I don't see why it wouldn't be safe.
I don't know anything about rays. But I have it in all of my cichlid tanks and my bottom feeders are fine. Two Raphael cats, featherfin syno, and plecos.
Don't try it! I've done it and it caused the rays to get small cuts and also get extremely inflamed on the underside of their disc. Definitely do not recommend!!!!
There are different grades of the blasting sand. The finest grade will be fine as it's more sand like. Only problem is if your running anything other than a sumo, the light sand will reek havoc on your filters.