PAR, PUR, PAS Article.

[NanaReefer]

Found this to be very enlightening.
http://www.aquarium-pond-answers.com/2012/03/pur-vs-par-in-aquarium-lighting.html

 

[Lenny_S]

Thank you @NanaReefer
That article was very well written, and it has many great references. I'm still at a pretty early stage of stocking SPS corals, so I'm going to make some adjustments based on what I learned from the article. I don't want to lose any of the pieces I have, but since they are just a small number of frags, this would be the time to experiment.
I'm running four AI Hydra 26's over my 60Lx27Wx24Tall tank, and my light spectrum has been in the 12K to 14K (I think closer to 12K) kelvin range. But it included a lot of the green channel and a lot of the white channel to get to that, which according to that article is pretty much useless for corals. In addition, despite extremely well managed water params, I get spots of cyano all the time. In one of the reference articles there was a great piece on cyano (http://www.aquarium-pond-answers.com/2006/07/blue-green-algae-in-aquariums.html). According to that article, the green/yellow visible color spectrum (among other things) promotes cyano growth and it seems to state that lighting is a primary cause.
I made the change last night from these peak channel settings (R-60%, G-60%, DB-70%, RB-70%, V-70%, UV-60%, W-70%) to this new set of peak channel settings (R-100%, G-5%, DB-65%, RB-80%, V-65%, UV-40%, W-60%). I kept the photo period the same, 3 hour ramp (up & down) and 6 hour peak. The logic behind those settings was to limit the green/yellow color, and boost the wavelengths that the article listed as being useful to photosynthetic chlorophyll A & B. I ran the peak settings this morning and took some new PAR measurements, they are only about 5%-10% lower than the PAR measurements taken from the previous settings. I can't measure it, but theoretically I should have the same or higher PUR with these settings.
I would say, just from a visual perspective, that the color temperature is closer to 14K now as it looks a little bluer than the previous settings. To be honest, I liked the look of the previous settings better, but depending on the effect this has on the spots of cyano I have in the tank and the coral growth/health, I may raise the green channel and/or the white channel to adjust the look.
I'll let the tank run this way until I see a result (either positive or negative) and post my findings to the thread. Thanks again and wish me luck. :)