I would remove the glass the glass tops to increase oxygen exchange and increase evaporation for increased lime water addition. If you don't dose lime water then evaporation is not an issue. Place the bulbs 5-8" inches from the water surface. The closer they are, the more salt spray will accumulate but it can be wiped off fairly easily. I currently have 175W MH
5" from the water surface. Glass tops increased the amount of heat residing in the hood. Removing them allowed the hood to stay cooler and allow a large increase in evaporation which allows me to maintain Ca
in the mid 400's with kalk
addition alone. A decided advantage in that kalk
keeps the alkalinity perfectly balanced to prevent pH swings.