Here's a thread that show's how I rig up my CFL's in order to save money...
since you have lights already going you wouldnt need this many and you could drop them further into the tank obviously to adjust the heat amount... it gives me a great daytime to nighttime drop becuase the heat pickup can be large.
just make sure you dont buy the daylight bulbs, while they put out more lumens they put off less heat so if heat is the goal... the warmest color you can get will be hottest
http://www.terraforums.com/forums/showthread.php?t=117384
since you have lights already going you wouldnt need this many and you could drop them further into the tank obviously to adjust the heat amount... it gives me a great daytime to nighttime drop becuase the heat pickup can be large.
just make sure you dont buy the daylight bulbs, while they put out more lumens they put off less heat so if heat is the goal... the warmest color you can get will be hottest
http://www.terraforums.com/forums/showthread.php?t=117384