20k vs 14k bulbs

What wattage?  What fixture/bulb type?

jcom wrote: What wattage?  What fixture/bulb type?

Double Ended 150w

that's a neat website, but it's a pretty low sample of bulbs. Where are the PAR values being measured? Bottom of the tank?

I'm also curious about growth of corals with different bulbs.

My other thought is to go with 10k bulbs and get more acitinic bulbs to counter the white. Then I get good growth, PAR and good color.... just wish MH bulbs were cheaper. 

In general, the higher the Kelvin rating (the "k" after the number in a 10K or 20K bulb) the less PAR a bulb has. PAR (Photosynthetically Active Radiation, I think) is basically the  amount of light energy released that corals can actually utilize.

Edited by BobC63 - October 01 2010 at 9:26pm

BobC63 wrote: Personally I think people give too much weight to PAR alone.

I have grown coral just fine with a 20,000 Kelvin MH bulb. The coral farming tank was not my display. It was too blue for my eyes.

Keep in mind that a PAR meter that was developed to measure the light needed by plants growing in the world of air and dirt. The other world, "The Deep", where marine Zooxanthellae Algae live, is different. Zooxanthellae algae grows good just on the bluish light that reaches it through the water. Water absorbs most of the red end of the spectrum so, except for the SPS in the surf zone, light from the blue end of the rainbow is the biggest portion of what coral need to grow. It has been found that the red side of the spectrum is needed by Zooxanthellae but at a much lower intensity. The complete rainbow of color is mostly for our enjoyment.

I agree with everyone that there can be benefit to using a combination of MH and fluorescent lighting. Some light is for growth and some is for looks. There is not much shimmer past the surf zone. You might almost say that the light we see is what the coral does not need.

Here are some pics that Jacque Cousteau published for me to illustrate my point...









Look how quickly the yellow, orange and red disappears! In fact, the red was already pink in the surf level. 
It's my understanding that most of the coral we keep comes from depths 10 to 100 feet down.
MH lights are so intense, meaning they put out so much light, that even 10,000 Kelvin bulbs, which have a lot of yellow, orange and red, still grow coral really well. This is because they are also very intense with bluish light, the side of the rainbow needed by coral.

The newly developed T5 multi-colored combinations are addressing the corals need for the correct parts of the rainbow. Hobbyists with all T5's are seeing good growth and intense color. Some of them add the comment that their tank does not look as bright as it did/would with common MH lights. Neither did my 12" deep coral farming tank with the single 400W 20K MH hanging 8 inches above the water.

My 2 cents


Edited by Mark Peterson - October 02 2010 at 9:38am