Window screen light filter - Page 2 - The Planted Tank Forum
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post #16 of 29 (permalink) Old 08-14-2011, 12:47 AM
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There are some times that lower PAR can appear "brighter" to our eyes than some "higher" PAR situations, but it's never comparing apples to apples and there are always intervening variables that make a mess of trying to predict it.

My 11g and 45g are both LED lit but using very different LED combos and driven at different drive currents.

The 11g has a PAR of about 30 on the sandbed and it appears quite bright to my eyes. Yet my 45g, which also has around 30 on the sandbed, looks pitifully dim.


I'm not entirely sure of why this is. If I crank the LEDs up on the 45g such that it looks bright to my eyes, I get algae hell.



I'm not sure how "green" registers on a PAR meter, but our eyes are way more sensitive to green light than plants are, so a green light that's ludicrously bright to us may not be all that useful to a plant. You'd think that this means "lower PAR" on lights high in the green area, but this is just a guess.
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post #17 of 29 (permalink) Old 08-14-2011, 09:28 AM
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One benefit that I use the window screen for is to shade part of my tank from the High light that some of my plant like / need and give my low light fish a place to hide from it.

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post #18 of 29 (permalink) Old 08-14-2011, 10:55 AM
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I am so pleased I bought the window screen the other day, thanks to Hoppy. And, according to him I reduced my lights about 30 to 40%. My 55g is looking a little dimer now but, who cares. Btw, I use 2 54w Geisseman on this tank, about 10" from top of tank.

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post #19 of 29 (permalink) Old 12-06-2012, 04:24 AM
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Hi guys, I found this thread so I just continue here...

Something is odd about the spectrum of my Finnex 36" LED light using the window screen. And I just notice I bought the grey instead of black screen. Do you guys think its because I'm using grey screen the light spectrum went out of wack like this?



Two screen on


Two screen off




The same thing happened when I only use 1 screen.
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post #20 of 29 (permalink) Old 12-06-2012, 05:20 AM Thread Starter
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It looks like you are getting a diffraction effect that makes those bars of light show up. I haven't tried the screen with a LED light, so it may not work the same way. All I know is how it works with fluorescent lights. But, when you start shining light from near point sources through any form of "grating" you can get unexpected results (unexpected only to a non-physicist).

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post #21 of 29 (permalink) Old 12-06-2012, 01:02 PM
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I've been using black screening with Finnex fixtures and it works well. Takes 2-3 layers to accomplish what a single layer can do with a regular bulb-type fixture, though.
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post #22 of 29 (permalink) Old 12-06-2012, 08:15 PM
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Originally Posted by somewhatshocked View Post
I've been using black screening with Finnex fixtures and it works well. Takes 2-3 layers to accomplish what a single layer can do with a regular bulb-type fixture, though.
Do you get the light bars like I did?
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post #23 of 29 (permalink) Old 12-07-2012, 01:24 AM
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Nope, no bars.

What does your fixture look like when you place it over your tank while using the screening? Still get the bars?
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post #24 of 29 (permalink) Old 12-07-2012, 05:57 AM
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I have an AquaticLife 36" T5HO with one 6500k bulb and one Roseate bulb, I'm using 3 layers of the gray screen over my 12g Long. I'm only using the stock legs that came with the light to elevate it above the tank, so at it's highest point, the light is about 14" above the substrate, and at the lowest, about 8".

The tank has only been filled for one week, but so far so good. I'm debating on removing one layer of the screen. My photoperiod is 6.5 hours right now.

Thoughts?
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post #25 of 29 (permalink) Old 06-24-2013, 10:44 PM
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Quote:
Originally Posted by Hoppy View Post
We have been recommending using ordinary window screen to reduce the light intensity when you can't raise the light fixture high enough, but I had no idea how much the reduction would be. So, I bought a roll of fiberglas, black window screen from Home Depot, less than $5 for a huge piece, and tested it with a PAR meter on two tanks with two different lights.

Here is what I bought:



I set the PAR probe on the bottom of the tank, in the middle, and took a reading. Then I put one layer of screen on top of the tank, and took another reading, followed by two layers and another reading. Finally, with only one layer I lifted the layer up to the bottom of the light fixture to see what effect that would have.

Tank----no screen----one screen----one screen at light----two screens
15H------31-------------19-----------------19-----------------11--------
10-------43--------------26-----------------26-----------------16--------

You can see that one layer of screen reduced the PAR reading by about 40% and two layers reduced it by about 64%. And, it made no difference whether the screen was at the face of the light fixture or on top of the tank.

A different brand, type, or opening size screen might give different results, but this was the cheapest one HD had, so it's the only one I tested.
Ran into this thread after Googling "window screen aquarium light". Thanks for this info Hoppy. You mentioned in another thread that I created today that window screening would reduce light intensity by 40%, and it's good to find the source of your numbers.
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post #26 of 29 (permalink) Old 06-24-2013, 10:52 PM
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I'm going to try using one layer of screening and see how that works out. If the lights need to be dimmed even more, then I'll add another layer or two.
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post #27 of 29 (permalink) Old 06-26-2013, 01:52 AM
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How has everyone attached it or are you just placing it on the aquarium glass top?

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post #28 of 29 (permalink) Old 06-15-2015, 11:18 AM
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Originally Posted by nate2005 View Post
How has everyone attached it or are you just placing it on the aquarium glass top?

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Reviving an old thread. I'm curious about this too.
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post #29 of 29 (permalink) Old 06-15-2015, 12:20 PM
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Quote:
Originally Posted by GadgetGirl View Post
Reviving an old thread. I'm curious about this too.
Get a "kit" like this and make screens to any size.
http://www.midlandhardware.com/87565...Q#.VX7CFLGrPO8
You can make one the size of the top or one the size of your light..
Attaching it to the light is nothing more than strapping it to it..

Strapping it on the light face (or slightly suspended below, and made oversize to compensate for the light spread) would probably be preferable from a maintenance standpoint, unless you are doing open top and can use the screen as a top.

More depends on aesthetics and how hot your light is...

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Last edited by jeffkrol; 06-15-2015 at 12:32 PM. Reason: edit
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