Grim and I have exchanged info and found some variation with the exact PAR readings of the bulbs. I dont know if he has improved his testing methods to add more control to the testing environment, but I think its worth mentioning that even from one bulb to the next (same make, same model, same age) there is variation. I get higher readings for some Giesemann bulbs than ATI’s… he gets the opposite. I burn in my bulbs for 100 hours before testing, and then try to record at 18 months… he tests when they are pretty new as far as I remember.

What I want to convey is that while these are great sites, nothing can take the place of simply getting that info for yourself. A PAR meter is a VERY useful device that is slightly expensive (then again, so are pH controllers and test kits… which a PAR meter should be considered part of, if not easier to use). The cost of the meter will easily be made back by the insight you will gain as well as the corals you will likely prevent from death by its use. You will see that the numbers that these meters give… the ‘readings’, and the light that they are based on are always changing due to so many environmental factors that a truly quantitative comparison is very hard to produce unless you have lab-like conditions… and then how useful are those results considering how much the glass box with a water surface that is moving and has a tint will ‘screw’ with your exact results anyways? Just get a meter…