Does lighting grid or "eggcrate" signifigantly block light?

[LBCBJ]

I'm considering adding a sheet to the top of my 18g to prevent any fish from jumping out. Before I do so, I would like to get some data/info on how much light the eggcrate blocks. The tank houses SPS with a 150w halide so a large decrease in light transmission would be unacceptable. IMO it seems like eggcrate would block a signifigant amount of light (due to the numerous small squares that form the grid pattern) but I would appreciate any opinions and input on this

[blakeoe]

i used to use it and didn't find that it blocked any light. However it is "directional" If you put it one way the light will be focused in and the other way the light will be spread out.

[RichConley]

I think mine blocked 20-30% of the light. Mine didnt appear to be directional in any sort of way. It was exactly the same on both sides.


That being said, it is taking up surface area above the tank, so it IS blocking some light, wheter or not its acting as a diffuser/etc.


Anyways, there are MUCH better solutions. Try that mesh stuff used to keep birds out of fruit trees.

[HowardW]

Anthony Calfo stated in a thread here somewhere that eggcrate placed with the tapered side up will actually increase the usable light into the tank via redirecting and focusing the light into the tank that would otherwise be lost. He also showed tests to verify.

[LBCBJ]

Thanks for the input guys.

Rich - that's what I was figuring, about 20-30%, but I've never seen any data as I said before. How did you get that number? Did you use a meter or is that just a guess?

Howard - that's an intresting point, but I'm not sure if I believe that or not. Do you have a link to that thread? That would be very intresting to read.

Just looking at it with the bare eye, I noticed a considerable shadow effect when I placed the eggcrate on top of the tank.

[advena]

Originally posted by HowardW
Anthony Calfo stated in a thread here somewhere that eggcrate placed with the tapered side up will actually increase the usable light into the tank via redirecting and focusing the light into the tank that would otherwise be lost. He also showed tests to verify.

ive never noticed any tapering on the stuff i get from home depot... is there different eggcrate that i have never seen before?? do you have any more info on this tapered stuff?

would love to see that thread that Calfo wrote too...

-scott

[johns]

I got eggcrate from home depot as well and it is tapered. It's easy to miss the tapering as it's very slight. I didnt realize it for quite some time.

I've read some of the threads about the supposed increased light when using eggcate and I am VERY sceptical about it. I dont notice much difference by eye (probably slight decrease in light intensity with eggcrate on). But one thing I can measure is the temp in the tank, and it always goes up about 1 - 1.5 degrees within about an hour after removing the eggcrate. I'm pretty darn sure that if the eggcrate is reflecting away heat it is also reflecting light.

my 0.02

[advena]

thanks John...
i will take another look at mine...i had a feeling that would be the answer

as far as light increasing, seems unlikely to me as well (mainly due to the fact that the top edges of the grids would reflect light... dont see how you could have something inbetween a light source and its destination and increase the light... but who knows, which is why i would like to read that thread...

i also know that when shooting (still photography & esp. motion pix) you can use "eggcrate" on soft sources to give some directionality to that source...
this could either be good or bad, depending on your light arrangement & how much spread you rely on to fill your tank.

as far as the temp goes, that makes sense as long as your evap cooling takes place in the sump...

i will check out my eggcrate right now and check out the tapering.

-scott

[RichConley]

Originally posted by LBCBJ
Thanks for the input guys.

Rich - that's what I was figuring, about 20-30%, but I've never seen any data as I said before. How did you get that number? Did you use a meter or is that just a guess?

Howard - that's an intresting point, but I'm not sure if I believe that or not. Do you have a link to that thread? That would be very intresting to read.

Just looking at it with the bare eye, I noticed a considerable shadow effect when I placed the eggcrate on top of the tank.

It was visibly darker.

You have to realize, light is reflecting off of a TON of different spots on the eggcrate, and if its off to the side of the bulb, its reflecting 4 or 5 times. (its hitting the eggcrate at a shallow angle). Every reflection, you're losing 10%+ from that particular ray to heat. Also, PLENTY of it is just plain reflected upward.

[MJAnderson]

http://www.reefcentral.com/forums/sh...eggcrate+light

[RichConley]

MJAnderson

He means you'll get more light from one side than the other, not that it will increase total light. Its still reflecting a ton of it up, and converting a ton of it to heat.

When I put eggcrate on mine, all my SPS browned out.

[RichConley]

Read the posts. It only helps if you have REALLY REALLY bad reflectors. In most cases, the 20-30% loss is too much to overcome by the improved direction.

[LBCBJ]

Good conversation here guys. Thanks for the link, I'll check it out later tonight when I get a chance.

Can someone elaborate on this "tapered" eggcrate. I don't see any tapering on the piece I picked up at Lowe's today but mabey I'm missing something.

I wonder if it would be feasible to use a light meter to measure the lux or PAR under the eggcrate, if that makes any sense. I've never done an analysis of lighting so I'm not overly familar with it. Maybe this is something Sanjay could look further into since it is so commonly used.

To pose a basic question, why is eggcrate used for flourescent lighting in the first place? Is it to dampen the intensity of the bulbs, or to diffuse/scatter the light over a larger area? Maybe the original purpose of eggcrate could help shed light on it's effects when used on our tanks.

[RichConley]

Its to diffuse, hence "Lighting diffuser".

Its so that you can use less fixtures and less bulbs in a building.

[LBCBJ]

Originally posted by RichConley
Its to diffuse, hence "Lighting diffuser".

Its so that you can use less fixtures and less bulbs in a building.

Not to stray to far from my original topic, but if that is the case, then is it possible that it could work to the benefit of certain reflectors that have a pronounced "hot spot" (I know you don't like that term) by spreading the light more evenly?

[just dave]

As I read the thread linked the amount of light that actually makes it into the aquarium will be increased if positioned properly (thin side towards the light source) and if placed properly in relation to the light source (2.5"-3" from the bulbs) and while it was stated that even when used thin side towards the light that some light would be blocked the amount redirected into the aquarium more 'n makes up for this loss. That's what I gathered and it also seems these test were done with fluorescent bulbs.

I have a submersible light meter and plenty of egg crate so I may just run a little "test" of my own.

[advena]

still havent made it through the entire thread, but if it relies on junk reflectors, then there ya go...

i did measure my eggcrate (using some digital calipers) and the narrow side is 1.2mm and the thick side is 1.5mm...

think at this point im gonna keep my tank open top

-scott

[advena]

Originally posted by just dave
As I read the thread linked the amount of light that actually makes it into the aquarium will be increased if positioned properly (thin side towards the light source) and if placed properly in relation to the light source (2.5"-3" from the bulbs) and while it was stated that even when used thin side towards the light that some light would be blocked the amount redirected into the aquarium more 'n makes up for this loss. That's what I gathered and it also seems these test were done with fluorescent bulbs.

I have a submersible light meter and plenty of egg crate so I may just run a little "test" of my own.

oh... yikes! i use MH (250's)...
im not sure i wanna get mine 3" from the eggcrate!!

anybody using this with MH to "increase light" (and not to keep fishies from getting dry)??

which brings me to another question: i was assuming ppl placed this on the top of their tanks, and lights above that...
is it less effective (im sure it would be) to have the eggcrate mounted under a pendant thats like 8-12" above the water surface?

cripes here is the answer to my question, from A. Calfo:

You make an excellent point: indeed... for folks with halide fixtures that are rather high off the water, the egg-grate or like apparatus would need to be under the canopy itself just at (or only slightly beyond) the extension of the reflector to focus more of the light downward.

But for folks using fluorescents... the egg-grate can simply rest on top of the aquarium since fluorescent lamps themselves need to be very(!) close to the water (no exaggeration here... anything more than 2-3" off the surface of the water with fluorescents is a serious loss of light (intensity). Truly severe... the light meter does not lie

and even more info:

a fast response from Dana (big thanks to him for the effort in a very busy schedule of his own!)

but the gist of it is as we (proponents) remembered:

- his charts show an increase of 25% in the focussing area
- the egg-grate (parabolic louver) must be positioned properly: 2.5-3" from the pointsource of light/halides
- he did not see any significant improvement with fluorescents high off the water
- the egg-grate (obviously) does block some light

And (my) Cliff's notes version of the topic is (still) the same: egg-grate under typical/practical applications is a net benefit overall to most aquarists.


-scott

[just dave]

Originally posted by advena
still havent made it through the entire thread, but if it relies on junk reflectors, then there ya go...

i did measure my eggcrate (using some digital calipers) and the narrow side is 1.2mm and the thick side is 1.5mm...

think at this point im gonna keep my tank open top

-scott

I would think the reflector design would play a large part in if the losses were worth the gains.

[LBCBJ]

Originally posted by just dave
I have a submersible light meter and plenty of egg crate so I may just run a little "test" of my own.

I would love to see the results. I think I will also hold-off on the eggcrate until I can see some data. My fish will just have to keep their tails in the tank until then

[just dave]

The farther away from the water surface a light is the less effective (effective in regards to intensity reaching any given point in the aquarium) it becomes. In aquarium lighting the distances are often a compromise between effectiveness and practicality.

So to use the egg crate in its purposed manor it would need to be 2.5" to 3" from the bulb. To get the most light from your fixture into the tank this assembly would need to be as close to the water as possible (which is usually not practical.)

[just dave]

Originally posted by LBCBJ
I would love to see the results. I think I will also hold-off on the eggcrate until I can see some data. My fish will just have to keep their tails in the tank until then

I'll try it with my MHs in LA III reflectors and if I get real industrious I'll try it under different florescent fixtures.

[just dave]

I did try it on a florescent fixture with reflector (Coralife 96w Quad retro) and without getting into a lengthy post my results did not confirm that the light grid increased the amount of light getting into the aquarium at any point above or below the water surface. With the grid at the 3" distance from the bulb the best case I saw was a 11% decrease as the grid moves farther from the bulb the decrease becomes greater.

I'm in no way trying to refute DR's and AC's findings as I'm sure their testing was much more comprehensive and there are probably many variables that need to be considered.

One interesting thing I found was that a section of grid cut large enough to shield my SE 400w MH bulb in a LA III reflector held 3" away from the bulb had no impact on light levels. As the grid move farther away it had a noticeable negative impact. There is no way to use a section of grid that would cover the LA IIIs reflector and still get within the required distance of the bulb. I say it's interesting because if the grid can withstand the temps it could be used on this reflector to keep jumping fish from hitting the hot bulb. Probably not a real common occurrence but something that I've had happen on more 'n one occasion.

[LBCBJ]

Thanks for testing that out Dave! I just added a Flasher Wrasse yesterday, which are known jumpers, so I guess I'll have to use eggcrate until I can find a better idea