are you using a dome light fixture?, I used mine several times, with several differnt light names, some of which i bought at a dollar store, and by its self it would heat my tank up to 83-86, by no means am i saying it is better than a pet store bought infrared, but it deffinlty does the job for me for a cheap price. However a infrared lasts MUCH longer, the black wear out quick, i go throguh mabey 2-4 a month

CHONG