Is it OK to cover the the top of my tank with plexiglass, I think it's 1/8". I have a 120g reef tank with a 2x150 HQI MH and (2) 2x65 PC's. I would like to put the plexiglass between the top of the water and the bottom of the lights. I would also like to put plexiglass over the sump with the macro-algae. I'm evaporating water at the rate of 1-2 gallons/day. Are there any issue with light diffusion? Will the plexiglass get too hot? Any other ideas to reduce evaporation? Thanks for the help.