My terrarium has 2 CF lights on it and the canopy is closed. Ross is right, you need to get to the heat before it gets into the tank. My canopy is closed and without fans would probably melt the acrylic
, but I have three 80mm fans circulating and removing the air from the canopy and venting it out. Fans have speed control so by trial and error I vented enough air to get to the temps I wanted. I then have 2 additional fans in the lid of the tanks (under the canopy) to exchange some of the air inside the terrarium. These are mostly to reduce the condensation so I can see inside of the tank and are turning just at the threshold of condensation. Bottom of my viv is water, which also ads to cooling of the tank. I also have automatic misting inside. When it's all done - I actually have to heat up the water a little at the bottom of the tank to maintain the temps I want.