In a room that stays around 68 to 70 i have a 10 gallon for my hoggy. No uth just bulbs. With sixty watt bulbs the surface will be in the mid to high 80's through the day. I do use lamp stands so the fixture is not sitting on the screen. It has about an 1 to 2 inch standoff.

You may want to get a 50 or 60 watt and put them on a dimmer to see which works best. This way you could really dial it in.