I would also use the legs. I did have a compact fluorescent light strip on top of my glass canopy. The water temperature rose about 8 degrees by the end of the day. Also, underneath the glass got horrible white deposits from the water heating up like that and then evaporating against the glass. On another tank I did have the legs, and I had no problems with white deposits or heat build up. I then used short, stubby PVC
pipe for little legs on the first tank but I just got another light strip that will accommodate the plastic legs, since I felt that the legs made maintenance easier for me and kept the fish more comfortable too.