The Cobra will work fine, and a similar one that you might consider is the Ultratherm. I prefer those much more than the Zoomed or Reptitherm. You'll want to place it under the tank and never inside it, and it's a good idea to have a small air gap underneath the tank. The Reptitherm 500R will be okay, but I'd recommend a better one if you can afford it. The Johnson and Ranco thermostats are much more reliable, but the top of the line would be a Helix or Herpstat.