why the glass? it still will cutdown on your evaporation and impede the light. plus if you run a fan to evaporate your water [cooling] how will it do that with glass anywere? you don't need the glass just get rid of it. MH 8'' off the water is fine. with more evaporating comes better cooling[you'll need this in the summer] and you can topoff with more KALK for better coral growth and KALK also helps keep CAL,ALK in check and helps phosphate control [hair algea food!] M. HALIDES add heat so you'll need all the open space between the water and light you can get.
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