I love light. So much...
I am sure most of us are familiar with Photosynthetically active radiation, otherwise known as PAR. Basically PAR is the spectral range of solar radiation from 400 to 700 nanometers that zooxanthellae (the algae in coral tissues) are able to use to photosynthesize.
Most of us can go and borrow an Apogee PAR meter to measure the output from our light fixtures whatever they may be. The number that shows up on the meter is mol photons m-2s-1 PAR expressed as photosynthetic photon flux density or PPFD for short. So in a nutshell we can say "hey my light has a PAR value of 400 and that's awesome!" or my frag tank has a light giving off a PAR value of 60 that sucks" like [MENTION=7381]oredith[/MENTION] frag tank
I think most of us skip over PUR though. PUR is Photosynthetically Useable Radiation. This means the portion of the spectrum of light between 400 to 700 nm that the corals are actually absorbing and is useful to them.
Think of it like a big bowl of jelly beans that you are going to eat. If you are like me you hate those nasty black licorice flavored jelly beans. So they end up staying in the bowl. Not being absorbed by me. Same sort of thing applies here. Corals are going to absorb and use the light that follows along the chlorophyll absorption spectrum.
So lets say two different light fixtures may give you a PAR value of say 500 at 12 inches. What light is better? Well the light that more closely follows chlorophyll A's absorption peaks would be the best choice. That light will have a higher PUR value. So how do we determine this? Most fixtures, LED chips and lamps will have a spectral readout available on either the package or online. Take a look at and compare it to chlorophyll's absorption peaks. This will help you to determine what light may have the better PUR value.
As hobbyists we are always concerned with the health of our tanks and it always helps to be able to know what choices to make when it comes to equipment that helps them thrive. Knowing what light gives us a better PUR value is a lot more important than knowing the PAR in my opinion.I personally don't want to get into a back and forth over what brand is better than another. Hopefully this info can help us make that determination. Then you guys can have those discussions. Or just post chicken pics. whatevs....
I am sure most of us are familiar with Photosynthetically active radiation, otherwise known as PAR. Basically PAR is the spectral range of solar radiation from 400 to 700 nanometers that zooxanthellae (the algae in coral tissues) are able to use to photosynthesize.
Most of us can go and borrow an Apogee PAR meter to measure the output from our light fixtures whatever they may be. The number that shows up on the meter is mol photons m-2s-1 PAR expressed as photosynthetic photon flux density or PPFD for short. So in a nutshell we can say "hey my light has a PAR value of 400 and that's awesome!" or my frag tank has a light giving off a PAR value of 60 that sucks" like [MENTION=7381]oredith[/MENTION] frag tank
I think most of us skip over PUR though. PUR is Photosynthetically Useable Radiation. This means the portion of the spectrum of light between 400 to 700 nm that the corals are actually absorbing and is useful to them.
Think of it like a big bowl of jelly beans that you are going to eat. If you are like me you hate those nasty black licorice flavored jelly beans. So they end up staying in the bowl. Not being absorbed by me. Same sort of thing applies here. Corals are going to absorb and use the light that follows along the chlorophyll absorption spectrum.
So lets say two different light fixtures may give you a PAR value of say 500 at 12 inches. What light is better? Well the light that more closely follows chlorophyll A's absorption peaks would be the best choice. That light will have a higher PUR value. So how do we determine this? Most fixtures, LED chips and lamps will have a spectral readout available on either the package or online. Take a look at and compare it to chlorophyll's absorption peaks. This will help you to determine what light may have the better PUR value.
As hobbyists we are always concerned with the health of our tanks and it always helps to be able to know what choices to make when it comes to equipment that helps them thrive. Knowing what light gives us a better PUR value is a lot more important than knowing the PAR in my opinion.I personally don't want to get into a back and forth over what brand is better than another. Hopefully this info can help us make that determination. Then you guys can have those discussions. Or just post chicken pics. whatevs....
