Glass top causing heat?

[alimal]

Just set up my new system, I went from a 60g to a 220g. I finally got the canopy on which houses 3 400W 20K MH ...so now i'm wondering which would keep my tank cooler, having all 3 glass covers over the water and under the lights, or taking them off and have the fan that blows across the lights evaporate some of the water? There is also a fan down in the sump blowing into the water down in the cabinet. Any help would be appriciated.

 

[acrylic51]

Take the glass lids off and blow across the top of the tank.....Your not saving yourself anything by keeping the glass lids on to prevent evaporation......Your building unnecessary heat and cutting down on gas exchange at the surface of the tank......Evaporation is a good thing!!!!!