Re: [APD] Optimum Photosynthetically Active Radiation Values forAquatic Plants ? and relation to uW/nm/lm ?

["Richard J. Sexton" <richard at aquaria_net>]

At 04:17 AM 3/20/07 -0700, you wrote:
>PAR involves the what portions of the spectrum are emitted by a lamp.
mesurements like lumens or lux won't differentiate so long as the emissions
are within the spectrum visible to humans.
>
>Theoretically you could derive PAR for a given bulb if you had a measured
graph of spectral output and lumen measurements. But you will be hard
pressed to find the former for most bulbs.
>
>The way to get usable PAR measurements would be to measure with a PAR meter
at numerous locations within the aquarium and under the bulb. Measuring
directly below the bulb won't give a good indication of the actual useful
output because such a measurement doesn't take dispersion into account.
>
>However, any white light will serve well since white light comprises the
full range of visible light (or a balance or red, green, and blue spikes),
which, it happens, includes the PAR regions. And in particular, triphospor
fluourescents and white metal halides work very well.
>
>sh

Here's my take on PAR values for plant lighting.

Fuckit, use a brighter bulb and don't worry about it.

More than enough of the wrong light is better than a bit
of perfect light. The plants utilization of "wrong" light
is still very good. Use whatever bulb is on sale.






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