Originally Posted by
Ledman
http:///forum/post/3228638
I love the fact that every one is concerned about PAR but the real measure of light output Is PUR, which Is the Amount of USABLE light that is emitted by a light source. That is the true measure not to mention the fact that you water quality has an equal part in the coral growth equation besides your light output.
we could get a little more indepth if you would like. i was just waiting for a trigger to discuse some more technical aspects of light, growth and health.
PUR - photosynthetically usable radiation
PAR is a measurement of photosynthetic photon flux (area) density
(from wiki "Because photosynthesis is a quantum process PPFD is generally used by plant biologists, but W/m2 measurements are important in energy balance considerations for photosynthetic organisms"
PAR meter give us photon flux in a certain range of wavelengths and the unit of that measurement is PPFD. The PUR has to consider the actual photopigments involved (chlorophyll a, c2, peridinin for our uses mostly) and would therefore be more specific. PAR is more general, but still useful as it is easy to measure and compare.
PAR meters and lumen meter are much less expensive and are readily avail to folks like me.
there are other parameters that are probably as or more important ... like water quality, appropriate feeding, etc
the higher the light, the lower the nutrients have to be, otherwise you end up with lots of brown corals. apparently the xoozanthellae will overpopulate if you have high light with high nutrients and since they are green and brown it shows in coral coloration
some good reads and resourses use in my research. also some of these statements are summarys of conversation i have had with other members in out non profit organization.
http://www.personal.psu.edu/sbj4/aqu...osynthesis.htm
http://en.wikipedia.org/wiki/Photosy...tive_radiation
