Actinic

Actinic lamps produce light with a very heavy concentration in the blue wavelengths. This makes the light especially good for corals, anemones and other invertebrates, as well as some beneficial marine algae.
 
Actinic bulbs provide their spectrum in the range required for the the Photosynthetic process and health of Marine corals and Invertebrates and to a lesser extent freshwater plants. Actinic bulbs should not be used alone , but in conjunction with other full spectrum bulbs. Actinic bulbs are heavy in the blue light and can give everything a bluish tint.
Pulled it from this site..
http://www.badmanstropicalfish.com/basics/basics_lighting.html

jim
 
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