i currently have glass tops on my 150 gal. there are 3 tops because of the two support/dividers. I want to make a screen top for them because of the glass seemed somehow etched and won't clean off. anyway I also hear that the glass does not let the full spectrum through, and cuts down on the par. My concern is that all the screen kits have aluminum frames and corner pieces. Isn't aluminum bad for the water quality? or is it an issue since it's not actually in the water?? does anybody make the frames out of plastic?