Compact Flourescent are fine...Just make sure they have an all weather ballast or you can get some SHOCKING results and/or a short lamp life.....sick-lid boy said:You can get a compact mini fluorescent bulb. They are fluorescent bulbs that screw into a regular light socket. I have a couple in my 15 gallon and they work and look awesome. They should have them at most fish stores. I have the same one as in the link, plus another 18W with a bluish tint.