T5 over open water?

I have marineland 48" T5 lights.  It says in the instructions not to use over open water.
1.  Is it possible to use over open water without damaging the lights?  Maybe if I raise them up?
2.  I use standard covers (came with my All-Glass Aquarium) and they seem to have gotten a white film on them that I can't get completely off.  Does anyone have a recommendation on how to get the covers clean?  Thus far I have tried plain water with a plastic brush.

 

Cyberjester had great luck cleaning the lenses on his lights using CLR, but make sure to rinse whatever you clean with that stuff real good. I run my Current T5HO setup over open water, but it is made for that kind of use, however if your light isn't make to be run over a open tank it makes sense that it would be safe if there is no mist of salt water getting on it from microbubbles or powerheads pointed at the surface of the water.

 

pardon my ignorance, but what is CLR?

 

nevermind I found it. Calcium, Lime, Rust remover.

 

i had T5's on open water on my 55 but they had a cover over them. they were about 3 or 4 inches above the water and did just fine