So since the real costs with lighting are the purchase/start-up costs, monthly electricity bill, and bulb repacement to arrive at a targeted amount of light in the tank, it appears the issues becomes to ensure I get the light as efficiently into the tank as possible. A watt of light costs a watt of light no matter which approach, NO, ODNO or PC, is used. ODNO has the advantage of low-ish start-up and bulb replacement costs, a narrow hood depth profile and continuous light across the tank. The two ways, I can think of, to get more bang out of my monthly bill is to have nothing between the light and the water or at least clean the glass regularly (my preferance with kids) and to use as effective a reflector as possible. With the montly cost of wpg going so high (especially in Maryland this year going unregulated) I think I want to shoot for as low a wattage as I can practically get away with using my pressurized CO2 and ferts -- probably in the 2.25 - 2.5 wpg range with a quality reflector for each bulb. I now have about 2.7 wpg in my 40 gallon with a single reflector (Coralife's Aqua-mirror) for 4 bulbs. I've been very satisfied with the plant growth. What do you think about this?
I have a couple of other questions:
1. Does anyone have a source recommendation for individual 48" bulb reflectors?
2. What would be the ODNO configuration I should be thinking of now with, say a goal of around 170 watts? Eg, (((32 watts x 2 ODNO ballast)x .88 efficiency)x .75 heat loss) 4 bulbs = 169 watts. In other words: 4 bulbs running on two ballasts. I'm just guessing here and would like confirmation or advice.