frustration with lighting info

[davidm]

Due to no fault of the speakers, like JB at the symposium, but rather my ignorance, I am frustrated by the knowledge about what lighting is best for our corals.  Although JB compared different bulbs for their intensity, each bulb has different wavelength characteristics, with different spikes at different wavelengths, which of course make them appear more yellow, white or blue.  

 

which wavelengths are best for our corals?  It seems this would be as important as sheer intensity over the entire range of wavelengths.  As an example, a lot of folk claim excellent growth with radiums, does this mean, that despite their lower intensity over the entire spectrum of visible light, their spike at a particular wavelength enables good growth of corals.  Or do different corals, such as those with red or green polyps, do best under different wavelngths of light, making this question hopelessly complex?  TIA, David

[Aquariareview]

The basic as I got it from JB's study is this

 

A good bulb for growth is a 10,000k MH (like the XM)

A good bulb for color is the 20,000k MH (like the radium or xm)

[Gatortailale]

IMO a good bulb for growth is ........... Excellent water chemistry with calcium levels of 400+ and proper Alk & PH readings.  Beyond that, bulbs affect color of corals to some extent.  I have almost exclusively used 10k bulbs and been satisfied with both color and growth.  I do have a 400w 20k xm in center of my 125 and I must say, corals there do show more blue and purple tips on them.  But could also be 400w vs. 250 w (10k) on ends of the 125 that impacts color more than mere 10k vs 20k spectrum.  I see reefmons 4 x 400w 10k xms and they are VERY brite compared to my 250w 10k xm.  I just gave him some frags so will be neat to see what the 400w does compared to the 250.

 

Other factor, is that could just be personal tanks, bio & nutrient loads and source water w/ salt brand that impact coral color.  I have traded away a few frags of my green with deep purple rim cap and most folks say that after time, their cap does not have the strong rim as it did when they got it; even when they keep it under 10k.  Leads me to wonder if Tropic Marin salt I use impacts color; or if its the amount of food, or the heavy bio load I have.  In my 120 tank, I use IO salt and I see better polyp extension there, but some corals from the 125 don't have the same color in the 120.  To many factors I guess.  

 

I could go on all day with differnet theories about what makes corals have more or less color, but I'm no expert, but just like what I see from the color of my corals.

 

:rock:

[Sph2sail]

The core of JBs talk focused on Photosynthetically Active Radiation (PAR) as opposed to LUX (visible light spectrum).  Coral animals need PAR to feed the zoxanthellae to make the symbiosis work.  PAR is the simple way of saying "good" for corals.  How the PAR is allocated over the spectrum seems less important to the corals and more important to the humans looking at them.

 

Having spent time talking with folks about this, the 20,000K bulbs are really forcing coloration on the coral.  Not bad for the coral, but different.  As humans, we like the flourescingt colors and the brighter pinks/blues/greens instead of the "boring brown" (unfortunately, as a diver, my experience is that boring brown prevails).  Also, the 20,000K bulbs tend to put out less PAR, so the growth is measurably slower.  Some folks get frustrated with this and switch to a lower temperature bulb to get more growth.

 

Sunlight seems to be more even handed in spectrum allocation vs. MH bulbs.  If you looked at the spetrum allocation of the Iwasaki 6500K bulb, it was relatively even from blue to red.  It is the PAR champion and always leads in coral growth.  That alone should tell us something.  To my eyes, the Iwasaki looks a lot like sunlight.  When sunlight hits my tank, it is brighter than the Iwasaki's, but looks the same color.

 

Newer MH bulbs tend to bring more into the blue, forcing coloration of corals.  Regardless, PAR energy is required to make them grow well.  Hence the info on the XM 10K bulb sounds really good.  Maybe it is a good compromise between coloration of corals and PAR for growth.  I'm thinking of trying them out when my 'sakis run their course.

 

s