In most cases the fish will not get burned. As long as you have water moving around the heater it will keep it from making to much heat in one area.
As for a cover, this may cause some issues for ya. The thing is you will then block off the area and it will not be able to get much water movement. You could try some plexiglass around the heaters but put alot of holes in it. This way the water will be able to circulate arund the heater. I don't think I have really heard of a cover but other may have more ideas for you.
I don't believe the heaters would burn your rays, but if you want to try something you can use pvc. Take something like a 2-2.5" diameter pvc and on one end use a step down to make it small enough for a small power head. Once mounted inside the pvc your rays can't touch the heater and the power head insures that water is flowing over the heater.
It's actually quite easy for a ray to burn itself on a heater. They sit on it as the swim up the glass, it wont allow water to circulate around it, and they burn themselves. I've seen it happen a few times (some ugly cases too)
Ah didn't think of that. Of course I don't keep rays myself, but it makes sense that because of their shape they could block off a good portion of a heater.
The problem is, will it fit over your Stealth? I have a Tronic guard over a Ebo-Jager heater - however, I had to buy a "mis-size" because the Ebos are longer than the same wattage of Tronic, also thicker. It was a bit tight, but worked.
What about making some sort of cage for the heater out of hardware cloth? (It is like chicken wire except with 1/2" square holes) It would be cheap, and it should allow good circulation. I think it is made of galvanized metal, but they might have plastic coated versions...
Had 10 petwork dollars got 2 of those heater covers and they fit perfectly on the heaters. Thanx for all the replys guys. btw today is my first day of cycling my 75 using fishless method(first time trying this method) so wish me luck........220 coming soon hopefully b4 x-mas :dance: