The reason I suggested it is because I've kept rays for about five years and been here for awhile, and I've seen a lot of threads where a seemingly healthy ray goes south and fast. Ray's aren't like other fish they're skins pretty sensitive and they're very susceptible to stress and I've seen a ray eat till the day it literally died. No death curl no odd sign's in behavior just died and seen this in numerous threads here so I figured it was common and not worth the risk if a spare tank is accessible. Personally I like to be safe rather than sorry and maybe that's why I haven't lost a fish to anything other than unexpected predation in years. But as you've said it's your choice and you feel it's fine so again I wish you good luck.