Keith, if only the tubes died and the fixtures are still what you are going to use, you are stuck with whatever those tubes are (T-12/T-8/T-5). If 20 years old, I don't think T-5 even existed. If you are replacing the entire fixture, go with T-5 or even better, T-5HO tubes. You can't have too many lumens growing cacti. Tell me how much area (sq. ft.) and what sort of set-up you are lighting (shelves/floor/whatever).
