Quote:
Originally posted by jcltok
I have always wondered why hobbyists focus on watts. The real question is whether the coral is getting enough light - lumen. At sea level, the sun provides about 2650 lumen per square foot.
The other is PAR - you need 1800 microMol/m2/sec. Any quantum meter will show you. You have to be careful about lights that achieve high PAR by boosting the violet/blue spectrum at the expense of the rest. A balanced spectrum is needed.
You can define better or worse balanced spectrum by looking at the CCT. The CCT of many high Kelvin MH are around .26 X .26 which is too far away from a balanced spectrum. Certain deeply growing corals will do fine, but it makes it tougher to raise a larger range of coral.
A CCT of about .31 X.31 is more appropriate when you have corals that normally grow in a wider range of depths.
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Translated: "I just found reef central"
I think you can rest assured that everyone in this thread knows what you have posted already... you pretty much just walked into the car dealership and told the salesmen what kinds of cars they sell with that last post. Wattage does concern us though as far as what we spend on our utility bills. Being that large reef tanks are using more and more wattage, keeping track of how much we are spending on our reefs as far as upkeep is important.
Here are some websites that may bring you up to speed on where we are at...
http://www.reeflightinginfo.arvixe.com/
...Sanjay has also written a series recently, to fill in the blanks for anyone who didnt already know...
http://reefkeeping.com/issues/2006-02/sj/index.php
http://reefkeeping.com/issues/2006-03/sj/index.php
http://reefkeeping.com/issues/2006-04/sj/index.php
http://reefkeeping.com/issues/2006-05/sj/index.php
As you will see from that last article, your suggestion of a CIE chromaticity (not CCT) of .31x.31 isnt on the market. And CCT is something different, not given by coordinates like you gave.
You will also find that you suggestion of "2650 lumen per square foot" isnt a measure you can use. Lumens are used to give the total output of a bulb, its not used to describe light across a surface... that would be Lux or Footcandles. In reefing, we tend not to use the photometric scale though since its not an accurate measure of radiant energy. So we stick with PAR, or PPFD. 2650 lumen per square foot isnt really a guideline we can use, neither is 1800MicroMol/m2/s. At what point should we have 1800? At the bulb? At the water surface? At the coral? In nature, you get over 2000 at the surface in Hawaii in the middle of winter. The amount we put in our tanks should be much less than this though, at the surface, since our tanks are not 30' tall like in the ocean. If our tanks were getting 1800 at the surface, our corals would be killed, since our corals are from waters that are 5-25m of depth usually in the wild, and are used to intensities often no more than 300-400 (max of 700 for some yellow porites). So its not like anyone needs '1800'... Many tanks have PAR levels of over 2000 near the bulbs if halide (very concentrated light output), or 900 if a tube (T5s). These levels drop off to less than 1000 at the water surface usually, unless you have a very tall tank and need very intense halides (400s) to penetrate to the bottom. Under the surface, light levels usually are 500-600 at most in the first few inches under the water, and often 200 or less at the sand. So where are you getting this '1800' from?