Actinic Replacement

Actinic are not just for looks, corals need a significant amount of blue light. In some cases, blue is more important than the other colors you get in a white light.

So yes, I would definatly replace the actinics as often as the other bulbs. Theyre color spectrums many not shift as much, but their light output certainly drops off.

I'll disagree with slip a little on this. Actually, I'd say it's a little of both. Although it's true that the most important part of the spectrum for coral photosynthesis is the blue end, most high color temperature bulbs have enough blue to be quite effective. You could easily get excellent coral growth with a good-quality 10000 K lamp and no actinics at all. But you would see little of the fluorescent color of the corals.

And Id disagree with mog. Coral experts such as anthony calfo and eric borneman recommend more actinic than daylight. Usually 2 actinics for one daylight, or an even split 2 actinic 2 daylight.

slipknottin said:

And Id disagree with mog. Coral experts such as anthony calfo and eric borneman recommend more actinic than daylight. Usually 2 actinics for one daylight, or an even split 2 actinic 2 daylight.

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I concur...although a full spectrum day light will provide some 'blue" light, the actinics provide more light in the spetrum range that encourages photosynthetic processes and health needed for corals and inverts - that is why in many vho or pc fixtures, you see 50/50 daylight and actinic. Even when metal halides are used, many experts recommend filling in with some actinic lighting as well.

You know, I hate to think I'm insane, but maybe I am. When I look at Joe Burger and Sanjay Joshi's analyses of the spectra and PAR values of MH lamps, there is a huge peak in the blue region for 10000 k lamps. Adding a few actinic lamps is simply a drop in the bucket.

10000 K fluorescent bulbs also have a significant peak at the blue end, not just a small bump. I don't have Borneman with me, and find Calfo's prose too irritating to read, but are you sure they weren't referring to 6700 K lamps?

As with many topics related to fish keeping, lighting is very controversial...for a good pro and con argument, check out http://www.reefs.org/library/article/actinic_lighting.html - it is a discussion by various authors related to the importance (or not) of actinics - not necessarily conclusive (as if anything in fish keeping is ) but definately interesting...enjoy the article and enjoy your fish!

Thanks for the link. Looks like this discussion goes back a long way. But a lot of the discussion centered on 5000 and 6000 K lamps, which have very small blue peaks. The discussion of higher color temp lamps seemed pretty cursory.

Although I am trying to read it while doing an experiment, it looks like the upshot is "it depends." Depends on where the corals were collected, depends on the spectrum and intensity of the "daylight" lamps.

I'd be a lot more satisfied if someone actually provided data with regard to growth rates, but will now shut up, having said my piece.

As far as Pterois' original question, I'd agree with slip that the actinics are definitely adding usable light and should be replaced like any other lamp. There is certainly no harm, and there may be a benefit to keeping the balance 50/50 daylight/actinic, so why not keep it like it is.