I think it all depends on the viv. I have a 2 foot 54 watt power compact that is bright white. When I tried it over my 40 breeder, that viv got too hot, way fast, close to 30 degrees celsius. However, after recently completing a extra-tall exo terra build, I found myself cashless and unable to buy the 4-buld T-5 setup I wanted. Being that there are no frogs in the tank yet, I decided to try it out in the interim. The light put out is excellent color and reaches the bottom well (36"). I currently have a hodgepodge of lighting over the viv, 1 dual tube T-10 fixture with aquarium gro-bulbs, the single power compact, a singleT-8 striplight that gets hotter than the power compact, and a hydrofarm T-5 single tube striplight. The highest the temp has gotten has been 24.5 degrees celsius. And all of these fixtures are sitting ON the glass untill I can get my small canopy built. So, I don't find the temp, on THIS particualr viv to be extreme. However, on a smaller tank, absolutly.