# How much will eggcrate reduce light?



## JerSaint (Oct 22, 2012)

+1 on interest on the effect of eggcrate.


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## Hoppy (Dec 24, 2005)

I haven't been willing to buy a 2' x 4' piece of egg crate to test this, but that is what will be needed to find out what the effect is. I have even advertised on FreeCycle a few times for used pieces of egg crate, with no success. My prediction is that it will greatly reduce the light intensity near the ends of the tank, but not nearly as much near the center of the tank.


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## xmas_one (Feb 5, 2010)

I remember seeing something years ago claiming that the eggcrate actually _*increased*_ the amount of light making it into the tank. Granted this was a long time ago, and it was on a reef board (maybe even a BBS, yes, that long ago). They do sell chromed "parabolic" eggcrate, I don't imagine that they would go through all the trouble/cost to parabolize and chrome the grid if it was a purely cosmetic effect. I'll dredge around and see if I can find any decent links on it.


Here's what I got from a quick and dirty googlin': http://forum.marinedepot.com/PrintTopic24384.aspx


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## lochaber (Jan 23, 2012)

Huh.

I'm guessing that if it does increase the light, it's because any beam going towards the side of the tank is likely to strike the white (and thus, reflective, I imagine?) grid and be reflected/refracted more towards the center of the tank.

Although, I would assume this is highly dependent on the shape/orientation of the light source relative to the tank.


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## James M (Jun 21, 2012)

You're placing a physical obstruction in front of the light, it's physically impossible for the light to do anything but decrease.
It's sold as light diffuser for a reason.


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## lochaber (Jan 23, 2012)

James M:

I think it's more like the concept of a fresnel lens. It's not actually increasing light, it's just focusing it more towards the center.

That link has a neat little diagram of measured light levels with and without the egg crate, it's worth taking a look at.

Would also be worth doing some more PAR measurements for someone who has both a PAR meter and some eggcrate lying around.


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## James M (Jun 21, 2012)

There is some of that effect directly underneath the fixture, but there is also blockage, further the eggcreat itself absorbs light. The further you get away from the fixture, the more PAR loss there is with the eggcrate as opposed to no egg crate. That's why it's used to diffuse light I guess.


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## dmagerl (Feb 2, 2010)

Took my meter and put it in the center of the tank, put egg crate on top of the tank and the light dropped by roughly 20%, from 34 to 27par.

29g tank, 2 t5ho roughly 30 inches from the tank bottom.


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## Axelrod12 (Jun 28, 2013)

dmagerl said:


> Took my meter and put it in the center of the tank, put egg crate on top of the tank and the light dropped by roughly 20%, from 34 to 27par.
> 
> 29g tank, 2 t5ho roughly 30 inches from the tank bottom.


Awesome thanks a bunch. I was hoping someone had a meter and some eggcrate around. Any chance you have a couple cfl's in shop like domes?


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## dmagerl (Feb 2, 2010)

nope. Sorry.


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## Axelrod12 (Jun 28, 2013)

dmagerl said:


> nope. Sorry.


Haha oh well, worth a shot. Thanks though. Conditions are very close to mine at the moment too. I have a 29g as well, 2 t5ho with lights around 25" from the substrate.


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## jmsaltfish797 (Oct 27, 2012)

im using eggcrate on my 20g long to cut down light from a power compact light. it works fairly well to help cut down light, even right under the fixture. if one piece doesnt work you can always stack it and stagger the grids to increase the effect. im doing this myself and it works great.


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## James M (Jun 21, 2012)

This just in, other opaque objects such of duct tape across your light fixture will reduce the light rather than increase it as well.


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## Axelrod12 (Jun 28, 2013)

I'm actually using the eggcrate as dual purpose. When I get my third light back I might be a little too far high light. 

Also I recently got an African Butterflyfish for the tank and they are known jumpers so I wanted a lid that could cover all gaps. I just cut little holes for wires and tubes that go over the edge. My other option would be a versa top, but I believe they have gaps. Eventually I may switch to the versa top and use the eggcrate just to cover the gaps on the versa top thus allowing more light through.


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## Terminalance (Oct 31, 2013)

> My other option would be a versa top, but I believe they have gaps. Eventually I may switch to the versa top and use the eggcrate just to cover the gaps on the versa top thus allowing more light through.


Versa Tops can have 0 gaps. It's 2 pieces of glass hinged together with a a solid plastic piece in the back. It's not like one of those precut T12 hoods. It's easy to cut so its really up to how well you can carve out the plastic to fit seamlessly with your cords, hob, heater, c02, etc.


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## puopg (Sep 16, 2012)

I placed a window screen in front of my fugeray to reduce the light put out and i went from 70-35 PAR. So the eggcrate will probably reduce light no more than 50%.


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## Hoppy (Dec 24, 2005)

Thanks to wheaties1337 I now have a good sized piece of eggcrate to test. I hope tomorrow to see what effect it has on both a CFL light and a PC light.


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## wheatiesl337 (Mar 30, 2011)

Glad to help out. I'm looking forward to your findings.


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## Axelrod12 (Jun 28, 2013)

Hoppy said:


> Thanks to wheaties1337 I now have a good sized piece of eggcrate to test. I hope tomorrow to see what effect it has on both a CFL light and a PC light.





wheatiesl337 said:


> Glad to help out. I'm looking forward to your findings.


Awesome! Thanks a bunch wheaties. Great to get some additional data.


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## Idrankwhat (Mar 20, 2013)

we run LEDs on everything at the shop and egg crate type diffusers to keep in the jumpers on our reef systems. The loss of intensity VISUALLY is very minimal compared to the loss of intensity when we were running T5HO on all our reef tanks which "appeared" to be much greater. The loss was also very minimal on any tank we ran metal halides on. Not sure if the way the light is projected from LEDs or halides makes a difference though.


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## Hoppy (Dec 24, 2005)

Idrankwhat said:


> we run LEDs on everything at the shop and egg crate type diffusers to keep in the jumpers on our reef systems. The loss of intensity VISUALLY is very minimal compared to the loss of intensity when we were running T5HO on all our reef tanks which "appeared" to be much greater. The loss was also very minimal on any tank we ran metal halides on. Not sure if the way the light is projected from LEDs or halides makes a difference though.


Most people, me for sure, can't detect differences in light intensity unless they are very big differences. I doubt that we can see a difference of +/- 25%. But, LEDs do project their light in a different pattern than fluorescent bulbs do, so that could have an effect.


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## geesantoz (Mar 22, 2013)

Which eggcrate that you guys use ? Is this the one being used for reef ?


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## Hoppy (Dec 24, 2005)

geesantoz said:


> Which eggcrate that you guys use ? Is this the one being used for reef ?


This is the "eggcrate" that comes in 2'x4' panels for dropped ceiling installations where there are lights above them. It is white, about 5/16" thick, with about 5/8" square openings and 1/16" thick "ribs" forming the square openings.

I just tested it with a PC light, a 20" long, 36 watt bulb. The results astonished me! At the center, under the light, the loss is only 7%, with the eggcrate anywhere from right at the light to about half way down to the PAR sensor. Lower than that it drops the PAR a little more. At the ends of the bulb, centered front to back, the loss is only 9%, again with the eggcrate at the bulb down to about half way to the sensor. At the front, about 5" from the side to side center, centered along the length, the loss is about 8%, again with the eggcrate at the bulb down to about halfway to the sensor.

So, for long tubular bulbs we can assume about a 10%, or less, loss of PAR. I expected it to be about 50%.

I also tested it with a CFL bulb in a "dome" worklight reflector. The loss of PAR was 6%! I couldn't do an off center test due to the difficulty in maneuvering the eggcrate, the light, which was propped on top of two chairs. And, I only tested it with the reflector sitting on top of the eggcrate. I'm sure the off center, and variable position of the eggcrate tests would be about the same.

These are a great way to have an open top tank, without letting the fish fly out. Even a glass top on the tank cuts the PAR by about the same amount. The eggcrate is stiff enough not to sag, sturdy enough not to break, won't collect water evaporation scum, and is easy to work with. Home Depot has them for about $14 each, in 2' x 4' size, which can be trimmed to fit most common tank sizes.


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## xmas_one (Feb 5, 2010)

Good show, thanks for running the numbers Hoppy!


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## Axelrod12 (Jun 28, 2013)

Awesome! Thanks a bunch for doing the tests Hoppy, glad to know I can stick with the eggcrate without worrying too much about my lighting being reduced. I'm interested how dmagerl got a result of a 20% loss though.


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## Paxx (Dec 17, 2012)

Thank you Hoppy and Wheaties.


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## JerSaint (Oct 22, 2012)

Thanks Hoppy and Wheaties! Great to info to have!


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## geesantoz (Mar 22, 2013)

Thanks Hoppy,

I use the glass versa top but the hinges create a shadow in the middle which makes a single light setup placement limited. I hope that using eggcrate, it will diffuse properly so shadowing effect is less.

I think cleaning egg-crate will be a pain down the road, but as long as it is not blocking the light ... it should be fine ... :hihi:


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