Quote:
Originally Posted by smokinjoe42  Should I be running the actinic light longer, what is the purpose of this light? |
Unless you're keeping mostly deeper dwelling zooxanthellates such as low-light corallimorphs, or maybe azooxanthellate corals that don't need light and that you're sick of picking the algae/cyanobacteria off of, or you're trying to simulate a much deeper environment than the more commonly emulated ones -- all situations that could potentially warrant "actinic only" lighting in many cases! -- the "purpose" of
actinic lamps in most reef tanks (e.g. one stocked with typical and commonly available reef aquarium species) is going to be aesthetics.
*
The light from
actinic bulbs does tend to be at useful wavelengths for corals and other zooxanthellates (420nm to 480nm) so if you're going to use
actinic lamps you might as well leave them on all day (eg.
actinics from 7am-9pm and daylight lamps from 8am-8pm or something). I leave mine on for an extra hour or two at night so I can see what I'm doing when I nightfeed - my
Caulastrea sp. are really finicky and won't open until all the white lights are out. I still only replace my
actinic bulbs (T5s or
PCs) when I replace their "white" counterparts since they don't seem as susceptible to "spectrum skew" as they age even though they may get an extra 7-14 hours of use each week.
* For instance, you'll probably get less "OMG I hate yellow!" comments from ReefCentral members who come across pictures of your tank if you use at least one strong actinic lamp. 
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