I got a private message from GaryE and thought my reply might be of interest to others. Here’s the message:
I know you have done innumerable studies on the various different lighting packages available. Have you ever studied the effects of different coverings on PAR levels?
Specifically, I'm interested in the difference between glass top vs egg crate vs mesh type screens.
I started my tank with the standard glass tops that came with it and decided that I wanted to go to something more open, so I went open top for a while. I had a very nice little hawk go carpet surfing, so that was a bad option. I have since moved to egg crate (white plastic) and am not real excited about the amount of loss I can perceive. Just to the naked eye it seems to be quite a bit of drop in light level. Whether this is just a loss of spread or actual loss of PAR I don't know as I don't have a par meter to check.
Thoughts?
My reply:
This took a bit of lab work using an Apogee MQ-510 quantum meter and a ‘globe’ Cree 6500K LED as the light source.
Eggcrate material: There is ‘good’ eggcrate and ‘cheap’ eggcrate. Good eggcrate has a ‘thick’ side and a ‘thin’ side – this acts as a parabolic lens and can concentrate light. I wrote an article about this for FAMA in the late 90’s and found if that orientation could focus point source light as much as 25% - of course, there is a reduction in light outside of the focus area. I do not have ‘good’ eggcrate anymore - the stuff being sold in big box stores is the ‘cheap’ stuff. However, if you’re fortunate to have quality eggcrate – and if memory serves – light will be focused if the thick side is up.
I have only ‘cheap’ eggcrate, but found there is a difference between white and black material
Black eggcrate reduced light intensity by 20%, while the white by only 12%.
Glass: I used a glass cover made for an aquarium, maybe 1/8” to 3/16”. Light intensity was reduced by 12%. Bear in mind glass will often transmit ultraviolet radiation. Not much of an issue if you’re using LEDs, but could be if you’re using a metal halide lamp.
Acrylic (thin and thick pieces): Light reduced by 12%. Acrylic will absorb UV and will eventually yellow and possibly disintegrate (if it is thin.)
Fiberglass window screen material: Reduced light by 44%.
I know you have done innumerable studies on the various different lighting packages available. Have you ever studied the effects of different coverings on PAR levels?
Specifically, I'm interested in the difference between glass top vs egg crate vs mesh type screens.
I started my tank with the standard glass tops that came with it and decided that I wanted to go to something more open, so I went open top for a while. I had a very nice little hawk go carpet surfing, so that was a bad option. I have since moved to egg crate (white plastic) and am not real excited about the amount of loss I can perceive. Just to the naked eye it seems to be quite a bit of drop in light level. Whether this is just a loss of spread or actual loss of PAR I don't know as I don't have a par meter to check.
Thoughts?
My reply:
This took a bit of lab work using an Apogee MQ-510 quantum meter and a ‘globe’ Cree 6500K LED as the light source.
Eggcrate material: There is ‘good’ eggcrate and ‘cheap’ eggcrate. Good eggcrate has a ‘thick’ side and a ‘thin’ side – this acts as a parabolic lens and can concentrate light. I wrote an article about this for FAMA in the late 90’s and found if that orientation could focus point source light as much as 25% - of course, there is a reduction in light outside of the focus area. I do not have ‘good’ eggcrate anymore - the stuff being sold in big box stores is the ‘cheap’ stuff. However, if you’re fortunate to have quality eggcrate – and if memory serves – light will be focused if the thick side is up.
I have only ‘cheap’ eggcrate, but found there is a difference between white and black material
Black eggcrate reduced light intensity by 20%, while the white by only 12%.
Glass: I used a glass cover made for an aquarium, maybe 1/8” to 3/16”. Light intensity was reduced by 12%. Bear in mind glass will often transmit ultraviolet radiation. Not much of an issue if you’re using LEDs, but could be if you’re using a metal halide lamp.
Acrylic (thin and thick pieces): Light reduced by 12%. Acrylic will absorb UV and will eventually yellow and possibly disintegrate (if it is thin.)
Fiberglass window screen material: Reduced light by 44%.