I use two UTH's in a similar way but I do have a single black light that is 75 watts (my house is pretty cold.) My tank is as tall as it is wide so I need the high wattage to keep the ambient temps around 80. In a longer tank, 75 watts would likely be too much and would kill the humidity. The black light I have is from the hardware store and gives off next to nothing for light. My humidity stays at 60% with some damp towels on top of the tank which I soak every other day and wash frequently. During a shed, I put some sphagnum moss in the tank to up the humidity a bit.