[StirCrazy]

Originally Posted by midgetwaiter

A label saying "Full Spectrum" is not a good way to judge the spectral output of a bulb, there are no standards for this distinction. It only means that the spectral output is spead across the visual light range. A given bulb may output much more blue or red light than others and still be labled "Full spectrum"

Neither is the kelvin rating. It is mearly a comparison of the overall colour of the output to a reference source that is heated to that temperature. There are also no standards for this rating.

As a matter of fact, spectral output is dependent on many factors, including the ballast. The same bulb will have different output on different ballasts. It will also change over time as the phospor in the bulb ages. Blue output will usually change first as well.

So the answer is, it depends.

you know I am going to have to agree with Bob on this one.. a 10,000K bulb is not a day light bulb but rather a similar spectrum with a heavy dose of blue. even thought the def of full spectrum can vary as a rule any full spectrum bulb will have more than enuf wave lengths in the PAR zone.

Corals use more than just the "Blue" light they also use some of the green and tiny bit of the red. the range of light usable to our corals is 380 to 720 nm, so you can see it includes the blue, all the green and a bit of the red. this light is what people are referring to when they use the term PAR (Photosynthetically Active Radiation) which is the part of the light spectrum that is usable for Photosynthesis. So just because a coral receives filtered blue light in the wild, don't think that it has to have that or even that it will do better with that light. Granted on more intense systems like MH setups you might have to gradually adjust the coral to the new light as a 10000K bulb will throw off way more actinic light and other areas of PAR than a 20000K bulb will, but on a VHO or PC system this shouldn't be a concern.

Steve