Hi Shango, Here is a link to APC concerning light spectrum and growth. http://www.aquaticplantcentral.com/forumapc/general-aquarium-plants-discussi ons/55756-light-spectrum-plant-growth.html (You may have to cut and paste) APC has a forum just dealing with just lighting and plant growth. "mackers" comment on 5500k makes sense, the lower spectrum promotes flowering not growth. Maybe Paul, Erik, and some of our other "plant people" could share what they think? Roy _______________________________________________ GSAS-Member mailing list GSAS-Member@thekrib.com http://lists.thekrib.com/mailman/listinfo/gsas-member