The Zoo Med Coral Sun Actinic 420 Aquatic Flourescent Tube is a high intensity actinic lamp with strong emissions in the short wavelength region of the spectrum, peaking at 420nm. It promotes growth of zooxanthellae algae, essential for the growth and well being of all photosynthetic corals and invertebrates. This bulb simulates the short wavelength blue light which penetrates to reef depth in nature. Output closely matches the absorption peak of chlorophyll used in photosynthesis. Ideal for all marine aquariums or reef tanks. Zoo Meds line of fluorescent aquarium lamps are made in Europe for ultra high quality, color, and longer burn life. Effective up to 10,000 hours.