Actinic lamps emulate the softer shades of blue light found at dawn, dusk, and in deeper water. With a spectral peak at 420 nanometers, actinic lamps promote photosynthesis and cause corals to fluoresce in beautiful glowing colors. For use with saltwater and coral reef aquariums. True Actinic 03 Blue gives of lighting from the 420 nm range that enhances fish color as well as other organisms in your aquarium. This bulb also benefits chlorophyll-a by emitting light at the peak absorption spectrum.h