[Beverly]

My lights are either directly on top of the glass covers or a few inches above. I keep my covers on to prevent splashing water and condensation from ruining my lights. There is a gap at the back of each tank where gas exchange and evaporation occurs. I make sure there is a lot of water surface movement from my powerheads, so there is plenty of gas exchange. I also clean the glass weekly in the sink with tapwater when I do my water changes.