Yeah, I made a couple to go over my in- tank overflows to shield light from getting in. Worked great!! Now I don't get any algea in the boxes or in the teeth of the overflows. I usually had to clean the teeth every 2 weeks or so cause my water level would start to get right to the rim. Now I don't ever have to clean the teeth. I made it overhang the teeth of the box by about an inch and I get no algea there whatsoever. One of the better ideas I've had!! Now looking at the side of the tank, the boxes are nice and clean. Only things in there are sponges.