"Well this light bulb is definatly too weak to grow coral, Unless its a 2.5 pico-reef, Do your self a favor, and spend a couple bucks more for a PC light system, You will be much happier. For a Freshwater system (small at that too) this would be fine, but You dont even need actinic blue! And Please Do not attempt to grow saltwater specimens with this light bulb, remeber 5watts per gallon! (rule of thumb for saltwater coral) and You also shouldn't attempt a nano/pico-reef without trying a tank that is 30+ gallons. For a small Fish-only aquarium this would be a nice light."