MH height?

Discussion in 'Lighting, Filtration & Other Equipment' started by pod, Jul 27, 2009.

  1. pod

    pod

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    Can anyone suggest an appropriate height (maximum) that the MH should hang without losing its effects. Have 250W 14K for a 24inch deep 37 gallon nano. I decided to hang it because of the heat. I have BTAs (mid), some SPS (towards the top), LPS (throughout), softies on bottom. I hung it about 12 inches from the top, and I want to make sure that I'm not "losing" the benefits of the MH's.
     
    pod, Jul 27, 2009
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  2. pod

    Wes888

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    Every since I made the posts about hanging the light fixture high (120mm) to fit the fans, people have replied I hang the light too high. Every since I tested the light with a light meter and lowered the light (3.5"), other people have replied I hang the light too low. lol.
    Apparently, different people have different idea on what's the optimal height.

    Anyway, my take is that it depends on the reflector on the light fixture. Some light fixture like mine is at it's optimal to have it hang about 3.5" above the tank edge for the middle of the tank. An inch or two higher would lost 25-50% of the light. That was tested and measured in my tank with a light meter.

    The bigger light fixture that have a long focal length reflector, you can certainly hang it higher.

    Sorry, I think I only confused you more. lol
     
    Wes888, Jul 27, 2009
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  3. pod

    bjohanson1234 .........

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    I think what wes is saying is that it is different for each tank.
    So use trial and error so that you get the results you want

    Brian
     
    bjohanson1234, Jul 27, 2009
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  4. pod

    ndepratt Equipment Junkie

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    the standard is 9-12 inches from the top of the water. you don't loose much intensity through merely a few inches of air, it's all about the water, the extreme loss of power that occurs is due almost entirely to the water, as you lose intensity equal to the square of the distance traveled. don't be afraid to raise it up a little higher ;)

    a source is below... but i would like to point that the refractive index of air at standard temperature and pressure is 1.0002926 while the refractive index of pure water is 1.03330... we can easily figure in that the refractive index of OUR water is a little higher than 1.03330.

    "The problem with old reflector designs is that in order to keep the light inside the aquarium, the reflector has to be mounted very close to the water’s surface. Until now, reef keepers have habitually kept their metal halide bulbs 8”-12” from the water’s surface causing excessive heat, increased water evaporation, salt encrusted reflectors, potentially harmful UV radiation, and less room to work within our canopies. The main aspect of this review is to elaborate on why raising our reflectors away from the water can benefit our reef systems."
    Reefkeeping's Product Review - Reefkeeping.com

    lumenbrights are another story ;)
     
    Last edited: Jul 27, 2009
    ndepratt, Jul 27, 2009
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  5. pod

    ccCapt Reef Hacker Moderator

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    Last edited: Jul 27, 2009
    ccCapt, Jul 27, 2009
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  6. pod

    ndepratt Equipment Junkie

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    god i love that guy.
     
    ndepratt, Jul 27, 2009
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  7. pod

    ccCapt Reef Hacker Moderator

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    LOL You're too quick. I posted that, but wasn't finished putting in the links so I had to edit and fix it.
     
    ccCapt, Jul 27, 2009
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  8. pod

    ndepratt Equipment Junkie

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    i've forgotten about advanced aquarist.... now i have to go and really all THEIR articles too.... sheesh i need a life.
     
    ndepratt, Jul 27, 2009
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  9. pod

    Bifferwine I am a girl

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    I have 4 x 250 watt MH lights above my tank, and they hang about 12" from the top of the water. And my tank is nearly 3 feet deep. It just gets too hot if I lower them.
     
    Bifferwine, Jul 28, 2009
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  10. pod

    yote Ceritfied Mantis Hunter Moderator

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    My fixture with 3X 250 HQIs 14.000Ks and 8X 54watt T-5s is hanging right at 6" above the water with no heat issues unless the AC quits.
     
    yote, Jul 28, 2009
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  11. pod

    ndepratt Equipment Junkie

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    that's a complete light fixture though, which is very different. your complete fixture is basically a very large duct...
     
    ndepratt, Jul 28, 2009
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