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  1. #1
    Moderator Krugar's Avatar
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    Lighting Theory question

    I'm having a heck of a time researching this one so I'm hoping somebody here can help me out.

    Let's say I decided I wanted 250w of lighting on my tank. Would it be better to get 1 250w light, 2 125w lights, or 4 75w lights? (all numbers pulled out of thin air.)

    Why?

    I know from the plant side, 1 big light is bigger. Mount it on a rail & move it back & forth.

    How does this equate to the marine world?

    Cheers!

  2. #2
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    I doubt you'll get a 'best' answer.

    1) The usual watt rating refers to power consumption. The actual water penetration and PAR will differ between bulb types. One MH bulb is better for SPS, etc. than 4 VHO of the same total wattage. And different types of MH of the same wattage can also vary.

    2) You get different visual effects from 1 250W MH vs 4x75W VHO bulbs.

    3) Uusing more than one bulb may allow more options for color mixing (e.g. using supplemental actinics) and might allow for sunrise/set simulation.

    Look forwrad to hearing other views on this.
    Nick

  3. #3
    DAN
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    Krugar
    this is just my opinion ,but I wouldn't go with anymore than 2 unless u have a long tank .Every thing I read so far says 1 light for 2' square area . I'm tosing around the idea of getting 1 dual ballast & 2 lights cuts the cost &the room down a little I thinking 2 X250 rember more lights ,ther will be more heat/expense/less room!! DAN
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  4. #4
    Moderator Krugar's Avatar
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    I'm running under the assumption that all things are equal, just the power output of the lamps should change.

    Aslo I'm not trying to compare MH to VHO to PC.

    My other addiction is bonsai. I've used HID lighting for years with my tropical collection in the winter & from this point of view 4 x 250W MH lights < 1 x 1000W MH light.

    Granted for best effect you'd get a light rail that moves the light back & forth over a 14 minute period, usually at least 6' long.

    Without getting into too much technical detail, even though you could put the 250s closer to the plants, the penetration wouldn't be the same & the plants wouldn't develop as well.

    Getting back to reef tanks, I have tonnes to learn here.

    From what I've seen, having every corner of the tank lit up is not always desirable. A light rail might simulate the movement of the sun across the sky, but I don't know if this has any (benifical) effect on coral or fish.

    So that brings me back full circle. All things being equal, would you rather have 1 honking big light, or several smaller lights that added to approximately the same power output?

    And why?

    Cheers!

  5. #5
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    Most people have 1 MH bulb for each 2X2 area of tank. That seems to give good penetration and a 'shimmer' effect which is nice to look at. The wattage needed for the MH depends more on tank depth and type of corals to be kept than on other factors: the area of coverage is essentially independent of the wattage. From that perspective, I'm not sure that your question is answerable. The only way to make 1x1000 w MH do the work of 4x250W MH would be to place it much higher above the tank which would reduce PAR and make it quite undesirable. I think that you will find that water absorbs light much more strongly than air and hence the impact of increased height is greater than the inverse square law predicts.

    I've only heard of 1 or 2 people talking about light tracking systems. It certainly isn't mainstream. Most people who want to simulate different times of day use VHO supplementation or have timers to turn on some of their MH bulbs and then add the rest. However, the later would only make sense over a large tank.
    Nick

  6. #6
    Moderator Krugar's Avatar
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    Actually I think you did answer my question

    Cheers!
    There is nothing so permanent as a temporary measure.

  7. #7
    Senior Member CableGuy's Avatar
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    I think it would would be an awesome idea to place one big 1000W buld on a light track and have it move back and forth over your tank. It would almost simulate a cloud or large wave, over the section of the tank opposite the the light.

    The ocean has large waves constantly moving across the surface of the water, causing the light to dim and intesify in certain areas. I think the light track would simulate this in a sense.
    "DREAM LIKE YOU'LL LIVE FOREVER, LIVE LIKE YOU'LL DIE TOMMOROW"

  8. #8
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    krugar

    your missing a few points but your close. MH as stated lights a 2' square area. It is also a point source light and not like FLUORECENT lights. depth of tank is an issues as well and what live stock you want to keep. 24'' tank depth can get away with 250w halide every 2'. deeper than 24'' you should use 400w halides. 175w halides can be used normaly on shallow tanks [nano].

  9. #9
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    Here's my take on this..., short & sweet.
    4 x 250w = 1 x 1000w in heat and wattage, but not in intensity(par). So on a reef tank, it won't be the same.

    Some people have toyed with the idea of installing a track system, but IMO, these have been people trying to save money on buying what it takes to light the tank. They think they will have the same results with one light moving. On a tank, you also tend to want it to be aesthetically pleasing to look at and not always have a shadow/light moving around. If you use 1 light, you'll only be getting a portion lit at any given time. This can very much play with the day/night habits of fish and inverts too( not sure but speculating here). For example, many burrowing wrasses will bury as soon as it gets darkish in the room and not only when the lights go out, so a dark area in the tank may very well trigger them to bury.
    Lastly, the general norm is x amount of hours of light over a tank, but with 1 light moving and casting shadows, this gets cut dramatically and perhaps won't be enough for good coral health. IMO, it's best not to use a track on a tank. JMO now..., I too would like to hear some other thoughts on this.

  10. #10
    Moderator Krugar's Avatar
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    First off at least in the plant world, you're not saving money buying a motorized rail. A decient rail costs almost as much as a second light. It's done to improve the health / output of your plants.

    Most rail systems (for plants) are on 14 minute cycles meaning they traverse the 6' rail in that time. They move slowly enough that there's no sudden change in lighting. Expensive systems allow you to adjust the period, but usually it's to make it slower (from memory).

    Plants grow towards the light. If corals do as well this would have the over all effect of your corals growing straighter as each side would get an approximately even amount of light.

    Again I'm just making this up, but I would think it might be interesting to compair a system with 3 x 250W MH lights to 1 1000W light on a rail.

    Since the light moves so slowly, plants don't enter a night cycle between periods. As suggested it's closer to mimicing the movement of the sun / clouds in the sky. Perhaps a really sensitive coral might have issues with this, but what do they do if a big fish or boat passes by overhead?

    As to aesthetics, the light's not on all the time. Since it's a higher power you may want to only have it on for a few hours and those may be when nobody's home to see the tank. Out side of those hours, why not use NO / Actinics for your viewing pleasure? Perhaps even set up a dawn (NO & Actinics) noon (MH) / dusk (NO & Actinics) / night (moon light)cycle?

    Not cheap, but this was never about saving cash

    Cheers!
    There is nothing so permanent as a temporary measure.

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