chrisslc wrote: Doesn't the blue light reach the coral at a greater intensity than the same wattage light, the same distance, of a different color.

Yes I think your correct but our tanks are not very deep...  mine is 24" so the deepest coral is around 20" from the water surface.  I don't think in that short of a depth that the other spectrums get filtered out that much...  meaning our tanks are dominated by a full spectrum instead of just the blue.

Mark Peterson wrote: Isn't the real point here, what coral do I want to keep and what is the light spectrum and intensity in it's natural environment?

Not the way I see it...  My opinion is my tanks will never come close to their "natural environment".  I know we all strive to duplicate mater nature but the fact is we are trying to duplicate an ocean in an aquarium.  So, IMO, elevating above their natural environment in the areas we can will only help pick up the slack in the areas we are lacking.  That is one reason I run alk/ca above NSW.    

Adam Blundell wrote: I strongly believe in blue light, because of it's importance to plants.  Yes corals aren't plants I know.

What is its importance to plants?  I know macro algae is not a "plant" but I've read several times that a spectrum around 5500k will grow macros like crazy.

dianatabor wrote: I'm not going to stop now, since everything's doing so well.

If it's working for you and your critters I see no reason to change.  Besides, your actinics will last a long, long time….

Anyway, JMOs

• 7:00 am - Moonlites On (so I can enjoy the tank before going to work; I feed night-feeding corals now)


• 11:00 am - Actinic On


• 11:30 am - Moonlites Off


• 12:00 pm - Daylight On


• 1:00 pm - Actinic Off


• 8:00 pm - Actinic On

(This is usually when I feed phytoplankton and spot feed (every few days) my mushrooms, torch coral, frogspawn, button polyps, and gorgonian)

• 9:00 pm - Daylight Off

(This is usually when I feed my fish and sun polyps)

• 9:30 pm - Moonlights On


• 10:00 pm - Actinic Off


• 12:00 am - Moonlights Off

I strongly believe in blue light, because of it's importance to plants.  Yes corals aren't plants I know.  But I have recorded photosynthesis rates in corals before, and I am sure they are using blue light to excite electrons in the chain.  I bet I have some nifty graphs at home, I'll look later.

However, get this, if you have enough bright white light, then I guess you wouldn't need blue light because you may already be running at full photosynthetic capacity.  I just don't think many, if any, of us have that much light. 

Aside from photosynthetic properties, and asthetic pleasure, I still think blue light can make a tank look more "real".

Adam 

Does the fact that the blue light is absorbed less than other light create a benefit here? It seems here that coral does not care about wavelength but it does care about intensity. Doesn't the blue light reach the coral at a greater intensity than the same wattage light, the same distance, of a different color. Or, as a layman in light, am I misunderstanding the principles?

I think that it has yet to be proven that "blue" or "actinic" light actually stimulates coral growth or increase coral health.  I know people (like Marc Weiss) have stated that 420nm light increases coral growth, but I think this is mainly marketing.

In fact I have read many acticles that have shown that Acropora actually grows faster under 6,500K lights than under high kelvin lights.

And although I had not read the article by Dana Riddle I agree with what he said (thanks for the quote Jon).

For the lazy, here's some quotes from that article by Dana Riddle:
(the lamps compared were a 4000K philips bulb ($20) and the Sunburst 12000K bulb ($75))

This experiment’s results suggest information potentially valuable for hobbyists - that rates of photosynthesis were essentially the same under these two distinctly different light sources. Other than aesthetic value, there appears to be no advantage, photosynthetically speaking, in using high Kelvin lamps.

The implication of these results should be of interest to hobbyists; it suggests that lamp selection (with due regard to lamp intensity) may be based on appeal, whether that is price or the "look" it gives to a tank, without fear of hindering photosynthesis. Economy-minded hobbyists and coral farmers may find this especially useful. It appears that light intensity and relatively simple light measurements alone adequately judge lamp efficiencies within the context of zooxanthellae photosynthesis. This should not be construed to mean that all light sources are adequate for reef aquaria use.

Here's and interesting article...  read the entire article before making a conclusion...  http://www.advancedaquarist.com/issues/feb2002/Feature.htm

Intensity vs spectrum quality...  not a new debat but it's still being debated.  The way I understand things is the PAR rating on the bulbs is the key.  The 6500k Iwaski is supposed to produce one of the highest par ratings of all MH.  It is rumored that the 6500k Iwaski produces a greater coral growth than other bulbs for that very reason.  The 10,000k XM's are supposed to be just under the Iwaski's so now we have a "good growth" bulb in the 10,000k flavor.  The 20,000k bulbs are said to produce the slowest growth rate due to the lower par ratings...  it would seem to me if the bluer spectrum was really important to the corals that the 10,000k & 20,000k bulbs would produce more growth than the 6500k bulbs.

I understand the lighting corals get in the ocean is dominated by the blue spectrum but when it comes to photosynthesis (and that is what it all boils down to) all spectrums of light play a key role.  IMO, Since our tanks are not 20' to 60' deep our corals benefit more from a full spectrum bulb than a actinic.

I agree painted bulbs... 7100k PC etc will cause a drop in lighting out put.  I was happy to see the "true" actinic PC's come out. 

I run my 110g lighting schedule like this... 12:00pm actinics on... 1:00pm MH on...  9:00pm MH off...  10:00pm actinics off.

Mark,

  We heard the "sunrise/sunset" thing from someone before you came over.  We have been following your advise since and have pretty much beat the algae problem.  Thanks.   I really can't remember where we heard to use the blue lights as a sunrise/sunset.  Wish I could.  We also had been told that the blue lights are only for the viewers pleasure.  I am glad to know that they are necessary for the health.  Don't feel like we spent the money for nothing now.