Hi I have been keeping rays for a few years. Most fish are fine, but occasionally you will have some fish that will bite the tails. I just get rid of the fish and move on. Right now I have a cross hatch trigger, pink tail trigger, thread fin snapper, Emp. angel, and a bird wrasse without any issues. I used to worry about trying triggers with the rays but they seem to ignore the rays. In the past I also had a clown trigger and a queen trigger in there with them. I keep them well fed. Never had an issue.
The worst fish was a morish idol. The idol would chase the rays. The idol had no interest in eating the rays, he just did not like them and would bully them. The rays are the reason I put the tank together so if there is an issue with a fish, its gone.