Planted Tank VIP
Join Date: Jul 2002
Location: Victoria,British Columbia, Canada
CRI is the Colour Rendering Index. This is simply a measure of how accurately a bulb reproduces colour compared to direct sunlight (CRI of 100).
CRI has very little to do with how well a bulb grows plants.
In the past Bulbs that use da High CRI typically used a phosphor that was BAD for growing plants (typically found in bulbs with a CRI over 88). Nowadays this isnt really an issue.
I am going to have to dispute the other posts here as well. I do believe that many "aquarium" bulbs have value over your typical commercial bulb. They are certainly overpriced, but they are most certainly not commericial bulbs.
Many bulbs from GE, Phillips, Sylvania, etc around 6500k have a sprectrum that is fairly high in the green, and not in the red and blue where it is better for plants. Coralife, Hagen, URI, etc tend to artificially boost the spectrum into the red and blue providing more benifical light per watt then your average commercial bulbs.
Capt has the right idea.. If you can find the PAR rating for the bulb, that is ideal. If you can't, try to find the true spectral output.