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Thread: Mh lighting...

  1. #1
    Senior Member RaceFaceR1's Avatar
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    Mh lighting...

    Alright I'm currently building a new canopy to accomidate my new MH lighting...

    2 x 250W...

    Now my question is how high above the water does the lights have to be?

    Should I enclose my canopy on all sides? And put 2 fairly large fans?

    And do I need a to put a glass cover?

    The bulbs I'll be using are 250 Watts 14,000K ARC...

    Thanks for all your info (in advance)!


    Marc
    180G - Reef
    29G - Goldfish

  2. #2
    Senior Member jklink's Avatar
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    RaceFace, I run a 75 Gallon with MH's and I've got them ~ 14" from the water surface. I think the minimum they suggest is 10" and even that's a little close.

    The closer you put them will definitely affect how warm your water gets and also the amount of salt spray that you will have to clean off the glass of them

  3. #3
    Senior Member RaceFaceR1's Avatar
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    That is what I was looking for!

    Sounds good... So about 15"... sounds good to me!

    Marc
    180G - Reef
    29G - Goldfish

  4. #4
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    Cool

    15'' is pretty far away, most go between 8'' and 12'' I would leave some back of the canopy open. fans are a good idea,how are you opening the front and what reflectors/pendants are you using?

  5. #5
    Senior Member ak_sniper's Avatar
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    I currently use a 175W MH light over my 20L and a 75W VHO Super Actinic (10-12hrs day) at about 4-5" from the water surface with NO heat issues and my temp. is stable. I also have a 1/8" thick acrylic (yes acrylic!) piece covering my tank to prevent evaporation and splashing. I have 2 x 120MM fans pushing each approx 100cfm in/out of my canopy, 1 intake / 1 exhaust. I have had my setup running this way for over 3 months now with no issues whatsoever. My total canopy height is approx ~8".

    AK
    20G Reef Tank (Starting again...)

  6. #6
    Mel
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    Mine are 9" away from the water. Personally that would be the max I would keep them away from the water. It seems like a shame to have MH lighting and waste some of it above the tank. I have seen some people with the bulbs as close as 4" but that's too dangerous IMO.

    I had a heat issue the first day as my temp rose 3-4 degrees to 82 in 2-3 hours. I installed 2 PC fans in the hood drawing air in and the temp is actually lower than the normal 78 deg. I feel sure that I can get away with a single 3" 12 volt DC computer fan for my MH's. Maybe when I add the 2 VHO actinics I might get a bit more heat but I don't believe so. Oh.. and my hood is 50% open at the top but closed on all 4 sides.

    EDIT: I notice some guys are using a fan for exaust out of the hood but I don't think that salty humid air is good for the fan. Simple dust kills the bearings in these fans, I can only imagine what moist air would do. The fans are cheap tho, so I guess it really doesn't matter too much

  7. #7
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    I vote for 10" off the water and good reflectors. I really like PFO parallells for that setup. I bought them for mine and they were worth every penny.

    My hood is enclosed and I blow fans in from the two ends. I put 3" X 12" sofit vents on the top of the hood above the reflectors to let the air escape up

  8. #8
    Senior Member pwall's Avatar
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    I have my 2 400w MH lights about 8" from the top of the water, with reflectors above.
    No heat issues whatsoever, but my tank is behind the wall and thus the lights are not in a cabinet to keep the heat in.
    Regards,
    Patrick.
    Ottawa (Orleans), Ontario
    Yahoo IM: pwallnfld

  9. #9
    Mel
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    Bvoss, thanks for the tip! I never thought of sofit vents. I started by looking into metal cabinet vents which were quite expensive as I wanted to prohibit the light comming out of the hood but not the air. Sofit vents are ideal!

  10. #10
    Senior Member RaceFaceR1's Avatar
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    What are sofit vents?
    180G - Reef
    29G - Goldfish

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