just my 2 cents on the original post: i use a 60w ceramic heater in a dome (w/ dimmer) sitting directly on the wire screen top. yes, the dome gets very hot, but i can grab onto the top part to move it just fine (i have clamps but never bothered to put them on). the screen never gets hot to the touch and it keeps the temps in my 20L tank in the 70s / humidity stays between 30-50% depending on the amount of misting i do.