Sorry for your loss
I agree with those who said guard the heaters. While rays mainly stay on the bottom, they'll also swim up the glass. If you get another ray, defenitely guard the heaters and make sure the ammonia, nitrite, and nitrate are under control. I have a 120 with a male marble motoro and its being filtered by 3 xp3s with a 4th coming in the mail (each xp3 is rated for something like 180 gallons) and I still clean the tank twice a week to keep the water nice and clean. Rays are really messy and pretty sensitive to bad water quality, especially when they are injured.
How big is your tank?