Is it escential to have a cover on your SW tank? I would like to but mine had none when I got it. It is a wood framed tank and the brace had broken so I replaced it but it is off center so I am kind of at the make your own stage. I would rather not have a cover at all but will that cause to much evaporation? Also would it cause the light to heat the water up to much? The one I made is out of plexglass and it really bowing down so its going to have to come off. I worked really hard on it too. Oh well.