that does still seem quite a good amount of reduction in electricity consumption though.
If I am understanding right, you measured the 40% reduction in power consumption at 50% dimming with the Kill a Watt meter.
My tank is 36" wide and although I get reasonable PAR with the existing units (40-50 at substrate, 30 at the extremes)when all tubes are on. Bearing in mind the lights are raised 3.5ft above the substrate.
I did wonder if two 8x54w units would be better in terms of visual light spread, colour rendition and I could even lower the lights. It is a lot of money though. So it is good to know that if I reduced the intensity the power utilisation would drop substantially.
I dont know if you have seen anything like this on your units but, I bought these ATIs in July 2010 and I am still using the same tubes, the PAR out put has dropped significantly. I used to be able to get 30-40 PAR and 25 at the extremes with just half the tubes on, the other day I measured it and it was around 20. Part of this could be down to more vegetation, but that would only be a small part. I thought fluorescent tubes dropped only around 10% in thier life time, maybe that was not PAR.
Last edited by sanj; 11-24-2012 at 02:52 PM.