ATI 39W Blue Plus T5 HO Fluorescent bulb combines the properties of a blue bulb (approximately 460nm) with an actinic bulb (approximately 420nm) producing an intense blue light with high PAR numbers and a light spectrum that encourages both bluing in SPS corals and fluorescence in capable corals. Also helps balance out a washed-out/yellow hued tank. Recommend Use: as a supplement to metal halides or in combination with Aquablue Special, Purple Plus or other full spectrum T5 bulbs. Can also be used for dawn/dusk applications. (Similar to KZ Super Blue.)