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Pod Your Reef

Actinics: To run, or not to run, that is the question.



13 members have voted

  1. 1. How long should I have my actinic lights on?

    • Never
    • Random times, less than 3hrs a day
    • Random times, more than 3hrs but less than photoperiod
    • Full photoperiod

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The question is whether actinics will help coral growth or are just purely aesthetic? Currently my actinics run at random intervals during the day for periods of 1/2 hr to 1 1/2 hrs. I also run a 150 watt MH for 10-12 hrs every day. As for corals, All I have is a pagoda coral, some polyps, mushrooms, and a xenia. I also have a green hair algae problem, but I'm dealing with it sort of.

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The halides are all you need, but I like my actinics to add color... I turn mine on an hour before I turn on my 10k's, and turn them off one hour after.

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The halides are all you need, but I like my actinics to add color... I turn mine on an hour before I turn on my 10k's, and turn them off one hour after.

OP I think you'll find that most people with actinic lighting turn run them prior to, during and after the MH being on.


For example, I my actinics run 12pm-11pm and my MH runs 1pm-9pm.

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if having algae problem lower hours of light to maybe 6-8

Yea I agree with that. 10-12 hours of MH lighting isn't really necessary IMO esp if you have actinics you can run.

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Thanks, sounds good. I run my actinics 20 minutes before my MH turn on, and the same when they turn off, as well as sporadically throughout the day.

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i dont think yo should have them on random times.. you should have them on like 2 hours before your reg lights go on and 2 hours after they go off.. to kinda simulate the sun where it gradually gets more intense then less intense

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Actinics do have a PAR value and will help coral to grow, not like the whiter bulbs do, but will supply PAR to the coral.


Some actinics have substantially lower PAR values, but the 460nm "Blue Plus" bulbs (ATI) are usually used as actinics and put out a significant amount of PAR.




But yes, they definitely are beneficial to the coral. I would run the MH for 6 hours, and let the actinics run for 8-10 (depending on when you want to view them).

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all you need is 6 hours of the mh, that could be why you have hair algae. also, it's probably not a good idea to turn you actinic on and off, keep it on a set photoperiod. like 10 hours or so.

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I'm one of those weirdo's who really likes the look of an actinically lit tank (maybe that's why I like night diving)

My actinics (VHO Super Actinics) come on at 5:00am (I get up at 4:30), go off at 10 when the MH' come on, then back on at 4 when the MH's go off. Then off at 7 when NCIS comes on :D

It appears that the question of whether blue light is helpful to corals is beginning to be understood.

Summary: Yes, it is.

Excerpt from Advanced Aquarist, May 2009


Effects of Altered Light Spectral Qualities

We're beginning to realize spectral quality plays important role in the health and growth of corals' zooxanthellae and hence the coral host. More importantly, we are starting to understand why and how light quality affects zooxanthellae and host pigmentation.

Wang and his group of researchers exposed zooxanthellae isolated from the stony coral Euphyllia glabrescens to differently 'colored' light in order to examine the effects of spectral quality on the symbionts' reproductive cycles. LEDs provided essentially pure 'blue', 'red' and 'infrared' light. (Note that these results are probably not just applicable to light generated by LEDs, but to any essentially monochromatic light). See Figures 6-9.

In a nutshell, 'blue' light and a mixture of 'blue' 'red' and 'infrared' wavelengths were about the same in promotion of normal zooxanthellae reproduction (although the 'blue' light seems to be slightly more effective).

Exposure to only 'red' light significantly inhibits the productive cycle (is this the reason for the slightly less efficiency of the 'mixed' light?). Infrared light apparently plays no part in regulation of zooxanthellae reproductive cycle, and the algal cells remain in the G1 Phase with no DNA synthesis or mitosis.

Figure 6. Over 50% of zooxanthellae are reproducing (that is, in mitosis) at Hour 23 when maintained under 'pure' blue light for 12 hours. Lamps were off between Hours 12 and 24. After Wang et al., 2008.

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