Giesemann Super Actinic 24W 24" T5 HO Lamp 22 inches from end of pin to end of pin (for 24 inch fixtures/retrofits) The Giesemann Super Actinic emits a very strong, pure actinic spectrum, which generates a light white/violet effect in your aquarium that maximizes the fluorescence from your colorful corals. Ideal for supplementation of existing metal halide lighting. 24W T5 HO Lamp. Will work in any T5 fixture, as long as you are using bulbs of the same wattage and length as those currently in your fixture Recommended for marine and reef aquariums Increases the fluorescence effect of coral and shells