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T5 reflector - light reduction

Discussion in 'Articles' started by Squidly, May 16, 2009.

  1. Squidly

    Squidly Lifetime Members
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    I've got two 80watt T5's (10000k and AquaFlora) over my 60" long 100g planted tank.

    To date I haven't been using Co2, but am using Excel - but have terrible algae growth and many of my plants are shrinking or disappearing. I started on a regime of liquid ferts which helped some of the plants start growing again, but the algae remains an issue. Withing 2 days after a WC, I have a full bloom reappear with or without ferts.

    So it seems I've got too much light (and not enough Co2). Problem is that when using one bulb, the color isn't right (too white or red) and by my eye, there isn't enough light to grow anything.

    I am wondering if there is a diffusion material I could place over the fixture to reduce the light or something I could put on the reflector surface that wouldn't damage the reflector or cause a fire to achieve that same end?

    BTW - I've tried the 6700k with the 10000k and the lighting to my eye is far too yellow and blue. With the Aquaflora, I can achieve a nice balance of color that appears somewhat natural to the eye. I would've liked to try a 8000k bulb with the AF, but it seems they are only sold in the EU.

    Thank you
     
  2. wilsar

    wilsar Prolific Poster

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    using a strip of masking tape stuck to the tube works for lessoning the light output.
     
  3. Squidly

    Squidly Lifetime Members
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    That would be a quick fix, but I would think leave a nasty mess of burnt glue all over the bulb or the reflector. Thanks
     
  4. VaughnH

    VaughnH Lifetime Charter Member
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    Your eyes will tend to adjust to whatever lighting you use, and it will then appear "normal". That adjustment period seems like a small price to pay for reducing the algae problems you have. And, that tank isn't high enough to need nearly that much light - it is the length of the light rays that determines the intensity at the substrate, not the volume of the tank. You could use both bulbs, but raise the light fixture about 6" or so to reduce the intensity. That might be your best bet.
     
  5. Squidly

    Squidly Lifetime Members
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    Wish I lift the light easily but I've got a 100lb canopy to contend with. Because it is an acrylic tank, I'd rather not view the top edge. To fix, I'd have to buy a surround for my retrofit - not exactly economical nor asthetically pleasing.

    As for the lighting, it takes me a few seconds to swap bulbs and the difference in visual effect is fairly quick given the combinations I've tried. I was not keen with any single light bulb of any I've tried but of all those, the 10k was the most pleasing effect to me. With the 6700 and 10k bulbs (or dual 6700's/10k's), the red plants are devoid of their red color. Two Aquaflora and you end up with a very red cast. Two 6700's and you're going yellow mostly and with two 10k's you see a lot of white (with some yellow). I do a good bit of photography and photoshop editing so I'm rather keen to the color results if it makes a difference. On the other hand, I could be completely color blind lol.

    What is the ratio for T5 output vs T8/12 anyway? Maybe if we had something like that, we could adjust the WPG rule better. I've seen 1.5x which would put me around medium lighting which is my goal along with Co2.
     
  6. ibnozn

    ibnozn Subscriber

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  7. jeremy v

    jeremy v Guru Class Expert

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    Squidly,
    I wouldn't tape anything to your reflector or your bulbs, that is just asking for a tape residue mess later. I have had success using regular window bug screening. I am using the fiberglass type, and it can be found at any hardware store. You buy it by the foot and it is very cheap. I have a large DIY CO2 tank that I am experimenting with right now just for fun, and I lay a strip of screening on top of the glass lid (between the lid and my light fixture) and it cuts the light in the tank down the perfect amount for my needs. I don't have a light meter but I would guess it is about a 30-40% reduction by eye. I place the screen strip on the aquarium lid whenever I am changing out a DIY CO2 carboy so that the plant growth slows and everything in the tank remains in balance while the CO2 is relatively low for a few days as the newly mixed carboy gets going full steam. I would think this might work perfect for what you are trying to achieve.

    If you don't have a lid on your tank that you can lay the screening on, possibly just wrap the screening around the bottom of the light fixture and attach it to the light in whatever way seems best based on your situation. Heat should not be an issue with any fluorescent type of lighting since the heat from the light can just go right through the screening and out like normal.

    Have a good one, Jeremy
     
  8. Tom Barr

    Tom Barr Founder
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    I used metal screen for a 1000W metal halide reducer, we simply used several layers to adjust the intensity.

    I would had optted for a 400W HQI, but they did not want to switch the lights.

    Metal screen will not melt or smell.

    Still, I think adding some CO2 and staying low light is a good option if the EXcel/Easy carb is not working well for the plants.

    They other option is to run one bulb and then the other only part of the day, say when you are around to view the tank, run both and then only one or the other when you are not around.

    Screen is easy to add and attach.

    Regards,
    Tom Barr
     
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