Nice to hear from you Richard, I have been away from here a few yrs and one of my reasons for coming back was to wonder how you were doing. Aquaman45 had a sting ray sting his RTC and it took a few days to die, I think it was in the shop at wharf.
I have also read on here about an RTC making a taco shape out of a ray and swallowing it.
If it causes an issue you may need to re-home it or the other tank mates....always loved the RTC though.