My cheap lighting experiment.
Par meter report on cheapo Ebay 50 watt led 6500k spot lights. http://www.ebay.com/itm/6X-50W-High-...3D831265008303
Directly under the light 1250-1300 par depending on proximity to center of spot light.
6" under water- 345-550 par depending on proximity to center of spot light.
16"-17" under water at substrate 101-103 par
16"-17" underwater at substrate in shaded areas 75-82 par
Darkest corner in tank 16"-17" at substrate 62 par roughly a 6" area.
Notes: By using the meter I was able to identify 1 underperforming LED spotlight, I am assuming it is defective. It metered at 600 par under the light, which is nearly half the output of all the others. Surprisingly the par rating at the substrate is unaffected. I imagine this is due to the other spots spreading light and covering for the weaker spotlight.
All in all I am pleased. I am running a total of 10 of these spots on a surface area of 84'x 36', coverage is excellent. Visually the lighting is very appealing and natural looking. Beautiful ripple from the surface.
I used a meter to see how much these lights were actually drawing. While they say 50 watt, they only draw 25 watts a piece. From what I hear this is typical of Chinese lights. They will half the advertised watts. Why? I do not know.
Total advertised watts covering the 84"x36" tank 500w.
Total actual watts drawn to power lights for 84"x36" tank 250w
TOTAL SPENT ON ALL LIGHTING UNDER 250.00