Relax. Burns like these don't kill a ray if you got the rest of the perimeters right. I prefer a separate filtration chamber when i can put all internal pumps, heater, probes etc... aesthetically more pleasing and functionally safer.
I would not increase the temperature too much to prevent a bacteria bloom. Just clean water will do. The best thing about rays is thats 99% of the time thats all they need to heal themselves.
I swear more rays are killed by owners trying something funny to solve the problem than the problem itself.