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Discussion Starter · #1 ·
After reading many threads and articles, I have come to the conclusion that I still have no idea whether this spectrum of light is beneficial to photosynthetic corals.

Comments?
Steve
 

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i would say yes it is. why? becuase most of the light output is focused in the blue spectrum, very little of the total wattage is wasted producing other portions of the spectrum that aren't used for photosynthesis. mostly, i think aquarist use the actinic is for color preference more than anything else. sometimes mh can make the water look yeloish, adding a actinic changes that. jmo!
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Banggai Mommy
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I'm thinking that it's purely asthetic. Growth rates are quite high under 6500K MH, but it's very yellow. Add actinics, and the yellow becomes much more pleasing to the human eye. That's why we run them - because it makes the tank look good, and not because of some added spectral benefit.

Just my 2c,
Danielle
 

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I have a 250w 6500k iwasaki over a 30 gal hex....no actinic...I would like them for the appearance,(still trying to figure out room...) but my corals seem to be VERY happy without them and the appearance isn't bad, just better with a little blue....

I think personal preferance should/would be the deciding factor...
bob
 

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The reactions to this subject can be amusing. Eric Borneman has basically staked his reputation on actinic light being important. Dana Riddle & Miguel Olaizola wrote an article (here) which concluded it's intensity that matters, not spectrum. When Dana tried to join a discussion in Eric's forum, Eric blasted him (her?).

I think there's plenty of evidence that actinic light works. However, the evidence that it works better than white light is weak at best (per that article).

There's an argument that blue light is more natural, based on the observation that water absorbs the longer wavelengths more quickly. However, this argument is weak for a couple of reasons. First, most of the corals we buy were collected in shallow water, where they're lit by unfiltered sunlight. Second, while it's true that blue light penetrates deepest in oceanic water, coastal water contains a lot of impurities that absorb blue. Thus, the most natual light in a deep coral reef is yellow/green (lacking both red and blue).

Part of reefkeeping mythology is that reddish light stimulates algal blooms. I have yet to see any real evidence of that. My own experience indicates that sunlight works fine.
 

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Discussion Starter · #6 ·
Thanks everyone for your comments, this subject sure does have varied opinions:D .

Sat, I read the article by Dana and found it to be very compelling.

I currently run 5 Aqua Sun and 1 50/50 VHO on my tank going on the assumption that intensity is what matters.
Steve
 
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