water evaporation

[whiterose]

What is the acceptable amount of water evaporation in a 75 gal. tank? I lose about 2 qts. every other day. I don't have a glass cover because I heard toxix gases can't escape and they seem to get dirty real fast. I have noticed many set-ups without the galss tops. I have two fans that keep the water cool and overheating is rarely a problem.

 

[cmack]

What type of bulbs/Lighting? My evaporation amount increased significantly when I upgraded my VHO lighting to MH.
Could be a normal amount for your lighting, and Home humidity levels...