Thanks for the info Sam, thats been my modus operendi for the present time at least. I found a formula to compute how much light is needed while browsing info at "The Krib". After reading this I find that by plugging in different numbers for the distance between the lights and the substrate, I can determine the proper height to best use my watts/gal.,I think. Pease look at this and tell me if you agree.
"When calculating the amount of lighting you will need there is a general rule of thumb. First multiply the surface area of the aquarium by the distance from the light source to the top of the gravel. Then depending on the type of plants you desire multiply this by one of the factors given below.
Low light plants 0.08
Low to Moderate light plants 0.12
Moderate to Bright light plants 0.18
Bright light plants 0.27
This will give you the ideal watt hours of fluorescent lighting that you need. Divide this number by 11 and you now have the approximate total wattage of lights you need. Unfortunately this number may not be equal to what is available in bulbs so find the combination of wattage that will most closely match this requirement and adjust the available time to match the watt hour calculation.
Example: required watt hours is 1440, divided by 11, is 131 watts of power. since the closest is 3, 40 watt tubes we divide 1440, by the 120 watt total and we find we need 12 hours of lighting at this level.
Warning: A common mistake is to deviate greatly from the 11 hours of light to compensate for low or high wattage. If the light time exceeds 16 hours more wattage should be added to reduce this time, Or if the light time is less than 8 hours less wattage must be used to allow adequate time for photosynthesis.
When selecting plants also keep in mind that large center plants will shade the smaller plants under them and that higher light requiring plants should not be selected for small filler plants. "
I have come up with 26" above my substrate to provide good lighting for moderate to bright light requiring plants, 12x48x26x.18= 2695.68 divided by 12=224.64 watts. I have put off building my light enclosure until I finalize this decission. For now I set the fixture on two pieces of 2x4 turned on edge and run the lights 12hrs/day. Whats your opinion on this so far Sam?
Eheim pimp #128, 55gal 13x20x48, Eheim Pro 2227, CO2 injected, into the filter breather tube,4x 55w Pcs , 12 hr light cycle (sunrise/sunset simulated), Milwaukee SMS 122, faulty bubble counter replaced with M3 bubble counter..... moderately Planted, Plantex CSM+B and ferts
To steal ideas from one person is plagiarism; to steal from many is research