Acrylic lid and par loss?

[John3]

I have a friend running 2 Kessil A160’s over a 46g bow front tank. Because she has some fish that may jump and 2 curious cats she has a 1/4” acrylic lid. I have been trying to help schedule the kessils but I seem to be at a loss. Some people say they crank them up to 100% intensity and others say 50%. I feel like shooting through this lid which gets foggy and salt covered is adding another variable.

I have placed some frags in her tank from mine and it seems like most lps struggle and or die. They don’t bleach, they seem to loose tissue and then die. Softies are thriving. The water paremeters look good and are pretty close to mine. I just feel like it is lighting but I can’t tell if there is too much or not enough light. I’m inclined to say not enough because of the lids.

Paremeters are:
Calcium 430
Alk 10
Salinity 1.024
Ph 8.2
Nitrates 20-30

Thanks, John

 

[saltyfilmfolks]

Cheap test if you don’t have a par meter.

Lux meter. $15 on Amazon.
I have several professional lighting meters I use , intensity , color , and par now.

Set your intensity.(par) andsee what Intensity you get without it, though it and then Let it get dirty, test agin on the loss. And then split the difference.

I have acrylic lids too , on two tanks. One set gets Dirty, the other not so bad. Takes seconds to clean them anyway.


And I’ve never actually tested any of that stuff and and have seen no reduction in growth , visual appearance or any reason to test it.

The kesslil might actually look better and you’ll have less shading and won’t have to buy the diffusion think like for radions.

 

[Luno]

I would opt for mesh/screen cover over glass or acrylic lids.

If par is a question I would ask around join a local reef club as well as the benefits of joining guaranteed someone in the club has a par Meter or the club itself that would be willing to lend or bring it round and test with you.

Also as far as intensity it is tank specific what's good for one tank may not be good for another. You trial and error on your own tank and depending on your corals and other tanks corals. In saying that generally you start lower and ramp up to where your coral prefers. I have ran tanks hitting max 1000par and tanks hitting max 400par.

 

[Bronx19]

Acrylic is 92%, so you lose 8% given nothing else.

 

[oreo54]

Even dirty lids "only" lose about 15%...............
https://www.thekrib.com/Lights/lights-wozniak.html

 

[Dana Riddle]

I realize this is beside the point, but eggcrate is a much better choice for keeping things in, or out, of an aquarium.

 

[oreo54]

to complete this a bit.. Par losses are probably about the same between eggcrate and glass..

 

[saltyfilmfolks]

to complete this a bit.. Par losses are probably about the same between eggcrate and glass..

I’ll disagree.
Egg crate is thick. And I metered it once at home.
And I’ve metered Light thought chain link fence and window screens too. And a bunch of really weird stuff too. Lol.

 

[JoshH]

And I’ve metered Light thought chain link fence and window screens too. And a bunch of really weird stuff too. Lol.

Someone has WAY too much time on there hands

 

[Bronx19]

How does fly screen go?

 

[saltyfilmfolks]

Someone has WAY too much time on there hands

Lol. Kinda.
I’m paid to meter Lights. Have been for close to 30 yrs. way too much time yea.

How does fly screen go?

Not well, depending on density it can reduce intensity by 400%.
Acrylic , glass , and the common clear screening we use on tanks tops has little to no effect.

 

[Dana Riddle]

I’ll disagree.
Egg crate is thick. And I metered it once at home.
And I’ve metered Light thought chain link fence and window screens too. And a bunch of really weird stuff too. Lol.

I think we're discussing two different things - keeping cats out and fishes in an aquarium, & light transmission. For the former, my vote goes to eggcrate - it allows the aquarium to 'breathe' and doesn't require cleaning as often as glass or acrylic. Salt spray is usually captured on it, although some will make it through. If the latter, there are two types of eggcrate: 1. The cheap stuff at Home Depot at is simply a grating that hides the fluorescent (or whatever) lamps. Obviously, it is going to cut (attenuate) that amount of light transmitted. 2. Real eggcrate that acts a parabolic lens. To tell the difference between the cheap and good eggcrate, look at the thickness of the grating - if it's cheap, the thickness when looking at both sides is the same. If 'good' - one side of the grate will be thick, the other side thin. Flipping this eggcrate either focuses light or diffuses it. It does not increase the amount of total light of course, but it can focus it and create a spot about 25% higher than without it. Home Depot used to sell the true parabolic eggcrate, but I guess they found a less expensive source. Same with Lowe's.

 

[saltyfilmfolks]

I think we're discussing two different things - keeping cats out and fishes in an aquarium, & light transmission. For the former, my vote goes to eggcrate - it allows the aquarium to 'breathe' and doesn't require cleaning as often as glass or acrylic. Salt spray is usually captured on it, although some will make it through. If the latter, there are two types of eggcrate: 1. The cheap stuff at Home Depot at is simply a grating that hides the fluorescent (or whatever) lamps. Obviously, it is going to cut (attenuate) that amount of light transmitted. 2. Real eggcrate that acts a parabolic lens. To tell the difference between the cheap and good eggcrate, look at the thickness of the grating - if it's cheap, the thickness when looking at both sides is the same. If 'good' - one side of the grate will be thick, the other side thin. Flipping this eggcrate either focuses light or diffuses it. It does not increase the amount of total light of course, but it can focus it and create a spot about 25% higher than without it. Home Depot used to sell the true parabolic eggcrate, but I guess they found a less expensive source. Same with Lowe's.

I agree. And it is a bit specific as well.

I’ve made dozens of fixtures with most all types of crates. Had to calculate losses, spread, as well as Color temperature shifts. Not all blacks are the same nor are whites.

The first example , the manufacturer can provide several types of grid dependent on the application by request.

 

[Dana Riddle]

I should have been more specific - the eggcrate I'm referring to is the plain white, square grid stuff. I've never tested the black honeycomb or the silvered material.

 

[Crabs McJones]

Someone has WAY too much time on there hands

That's because salty is the Best!

 

[oreo54]

I’ll disagree.
Egg crate is thick. And I metered it once at home.
And I’ve metered Light thought chain link fence and window screens too. And a bunch of really weird stuff too. Lol.

OK exactly what are you saying here?



Only PAR data I found on "normal" eggcrate is 6-20% light loss..
Glass about 8-15%

I did "round" this out a bit..

Funny though.. every eggcrate is called a "diffuser".. really doesn't imply a focuser..

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

http://www.reefcentral.com/forums/showthread.php?t=676292&highlight=calfo+eggcrate+light&page=2
http://www.reefcentral.com/forums/showthread.php?t=901978

Be aware that there is some loss of output when you use an Egg Crate. The amount of loss depends on the narrowness of the cells, so a 30 degree Egg Crate will have smaller cells & less output than a 40 degree. However, it's usefulness in the difficult task of controlling soft light is too big an advantage to dismiss.

http://lowel.tiffen.com/edu/light_controls/egg_crates.html

 

[saltyfilmfolks]

OK exactly what are you saying here?



Only PAR data I found on "normal" eggcrate is 6-20% light loss..
Glass about 8-15%

I did "round" this out a bit..

Funny though.. every eggcrate is called a "diffuser".. really doesn't imply a focuser..


http://www.reefcentral.com/forums/showthread.php?t=676292&highlight=calfo+eggcrate+light&page=2
http://www.reefcentral.com/forums/showthread.php?t=901978


http://lowel.tiffen.com/edu/light_controls/egg_crates.html

Basically what I’m saying is, and building in Dana’s point , not all egg crate is the same.

Different dyes are used to formula white and also black.

Different crates also have different thicknesses.

One of my jobs back in the day was to take a Light of a known color value and test each one to see what the color shift was and what the intensity loss was.

Specifically, we looked for green shifts and red shifts.

To totally split hairs here.
One thing actually to look for on these par loss tests would be spectraly. If the white is formulated most commonly, the shift will be to red and yellow. Bumping the par, but but in one end of the spectrum, and perhaps compensating a bit for the intensity loss. Youd have to look at the Light used and the material. An led and a t5 will likely have different shifts btw because of the blending.

 

[oreo54]

Understood. and agree it's ALWAYS "complicated"..

Bottom line though, and regardless of spectrum shifts..Does "common" eggcrate block more PAR than glass? Less par?

Should we add the complication of a more "coherent" beam of light (i.e LED's) hitting plastic barriers?

One of the things I found was that PAR increased for lights w/ inherently poor reflectors..which would be somewhat obvious..and the lights had to be a certain distance
as well....
Second obvious thing is the taller the cells the more light loss due to stuff bouncing around inside and absorbance..
Egg crate "should be" poorer at transmission w/ LED's than clear glass.

Guess even my "averaging" is probably pss poor..
So for a strictly PAR metric.. doubt if you can beat glass.. until you really foobar the glass w/ salt/dirt...
Certainly not buying an increase in PAR w/ eggcrate w/out very specific circumstances..
Too much contrary evidence though most is a bit "qualitative"..
As I said only PAR measurements but Danas that "I" found show losses in the visible spectrum overall and from the quote above so does your industry..

No not considering gas exchange ect here...and not implying one is "better'' than another in a blanket statement ..

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 also tested it with a CFL bulb in a "dome" worklight reflector. The loss of PAR was 6%

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.

SEE post 15
http://wamas.org/forums/topic/26776-eggcrate-for-focusing-light/

My conclusions from this rather simple test are as follows:

• Egg crate blocks more light than it focuses in the direction we are interested in (that is, into the aquarium).
• Egg crate does reduce the light that spills out from the aquarium through the glass panels.
• Measurement deltas between EC Up and EC Dn measurements are extremely small. Further runs would be required to determine if there is a statistically significant difference between the two.

 

[Luno]

I’ll disagree.
Egg crate is thick. And I metered it once at home.
And I’ve metered Light thought chain link fence and window screens too. And a bunch of really weird stuff too. Lol.

I'm a mesh fan, say 1cm cube mesh, how do you think that compares to par loss compared to glass?

I guess the other thing depending is time of cleaning involved and has exchange but if you have a sump I would assume gas exchange shouldn't be of concern

 

[saltyfilmfolks]

I'm a mesh fan, say 1cm cube mesh, how do you think that compares to par loss compared to glass?

I guess the other thing depending is time of cleaning involved and has exchange but if you have a sump I would assume gas exchange shouldn't be of concern

I have some of the mesh, I haven’t metered it and , honestly I’m not going to. Lol. Like I said above , I have sometimes really dirty acrylic. So.....
That’s actually prolly the best thing you can use a far as light loss. It won’t get dirty.

It also won’t stop a cat. Hahaha.

Yea , I do worry a tiny bit on co2 and exchange with the thick acrylic but ,not bragging, I have very good ph. In the tank alone . A lot of coral sucking it in and blowing out o2 , and then the same with a big Fuge.

But in the winter they keep the heat in very well.