Like most things in life, it is all about balance. Too much light can throw the balance as much as not enough. You can get 6500K energy savers that don't use much power or give out as much heat. Heat is wasted energy and therefore money when providing lighting. You want heat on the bottom of the tank, not the top. I bought a 6500K bulb from the wharehouse which was 23 watts but equivalent to 110 watts incandescent and it was only a few bucks.