# Do you need high PAR?



## niko (Jan 28, 2004)

http://www.aquaticplantcentral.com/...tic-plant-club/88961-do-we-need-more-par.html


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## BruceF (Aug 5, 2011)

PAR/ PUR

PAR is the abbreviation for Photosynthetically Active Radiation in the spectral range of 400 to 700 nanometers. This is the range that is needed by plants and symbiotic Zooxanthellae algae which live in the tissues of corals, anemones, clams, and other photosynthetic life.

Without the presence of Zooxanthellae these animals would die as they produce 90% of the food requirements these animals require. Most photosynthetic life do not utilize the full spectral range that PAR covers but respond best to light in the PUR (Photosynthetically Usable Radiation) range.

This can be confusing to many as there are light fixtures and lamps that are advertised as high PAR systems but do not provide a spectrograph to see the spectral range at which the PAR level was derived at.

Photosynthetic invertebrates respond best to light that falls into wavelengths between 400-550 nm and 620-740 nm which is the PUR range.

A PAR reading of 300 and higher isn't as good as it appears if this reading is derived from wavelengths produced throughout the entire PAR spectral range (400-700 nm) as much of this energy is not needed by photosynthetic animals and is wasted energy. This is one reason why it is very important to view a spectrograph of a lamp or LED fixture before purchasing. This will allow you to view the wavelengths of which a PAR meter will actually measure. A PAR reading of 150 at the deepest part of a tank will promote growth of all but the most light loving corals provided the lamp or LED falls into PUR range stated above.

A common misconception with many hobbyists is that they will say

"my new LED light isn't as bright as my old metal halide light".

LED fixtures tuned to the PUR wavelength use wavelengths of light that are the least sensitive to our eyes in terms of brightness even though these wavelengths are intense to corals and other photosynthetic life.

This is a good example of why you do not want to look directly at a UV germicidal lamp.

It does not appear bright to your eyes because of the wavelength, but the damaging rays are very intense and can have a negative impact on your vision.

http://orphek.com/about/kelvin-lux-lumens-par-pur/


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## Yo-han (Oct 15, 2010)

Depends on the plants/corals you try to keep. You can't keep some Eriocaulins with low PAR for example. Some prefer higher PAR or they lose their lower leaves. But I think high CO2 is more important than high PAR.


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