HEP Replacement Ballasts for Aquatic Life 4-Lamp Hybrid T5 HO lighting fixtures. When replacing a bad ballast, it is best to wait to disassemble and remove the bad ballast until the new ballast arrives and then swapping out will just take a few minutes. These ballasts are not dimmable. 24/39 Watt for 24" and 36" Hybrid Fixture, Item 470549. These ballasts can be used for other fixtures such as ATI, and retrofit kits. Wiring diagram is printed directly on the ballast.