The only thing I'd add is to make sure there's still some gaps between the cover and the tank. You don't want to suffocate the entire thing as obvious as that sounds. I leave an inch on both front and back of the glass so it can still get air in it... I actually have the top on for different reasons than evaporation (to stop the cat from drinking it and to retain some heat for my CRS as there's no heater in there). You'll be able to slop evaporation but don't think it'll completely stop it from happening as you'll still need to add water or just do water changes even with a top on.