Best Height for MH light

[Mark3]

I am going to be doing a little remodel on tank. Question: What would the ideal height for light above tank, building hood with 3 x 150 MH lights and 2 x 72" current orbit led strips.

I already have the lights, so that is not in the options, just the height.... in my build I could have them from 5" to 17" but not adjustable height once built.

I think I want them at least 7 or 8 inches for clearance/access to tank ... and thinking 17 is to much loss of light. I guess that is my real question, = how high can I go without losing too much par?

The current lights are the old ones, not the new orbit PRO witch have a lot more power.
The tank 125 gal ...22" deep ...surface of water to top of sand bed is about 18"

Anybody have an idea of par if lights are set at 9" above water?

 

[hybridazn]

I wouldn't go any higher than 8-9" with halides. Any higher and your really just wasting light.

 

[saltyfilmfolks]

im at 22,000 lux with a radium blue 150w MH. Lamp is 9" above water.
22,000 lux / 51(constant) = 431 par.
lux conversion constants
http://www.advancedaquarist.com/2008/2/review

apogee gives a constant of 71 but does not specify globe color(weird). so Im calling it 500 par in my tank.

my other fixture im not using is much more efficient and gives more intensity. so with a lux meter you can check the intensity of the fixture dry and est the par.
and yea 8 or 9 your prob good. as the light overlap you will get more intensity. 35,000 to 40,000 likely. Imo

 

[Mark3]

Thanks for your info....I think I will most likely set them at about the 9" height. Need a little room to get access into the tank.