# Par



## Bryeman (Aug 24, 2009)

Does anyone know of a good link or maybe can just list what's generally considered a good starting point for PAR requirements for carpet forming plants like glosso, clover, etc.? I saw one a while back, but can't find it now. I know the plants will ultimately tell the story on what's happening, but just looking for a good starting point for a hi tech setup.


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## TropTrea (Jan 10, 2014)

First off let me say spectrum is more important than PAR numbers. 

For fresh water plants 95% light is utilized between 400 nm and 490 nm as well as in the band of 650 to 700 nm. This is roughly a 140 nm band width while par meters measure all the light form 400 to 700 nm for bandwidth of 300 nm. Some light sources are strong in green light so you can get false reading on PAR caused by high amount of green light. On the other end most PAR meters loose there sensitivity to blue light so might have a lot more good created from the blue light than your Par meter is telling you. 

If you have a good spectrum with a roper balance or red and blue light then generaly good results are obtained with PAR reading around 80. But with a pooor spectrum that is heavey in the green range of the power spectrum even a PAR reading of 120 could fall short of the needs of your plants.


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## whiskey (Oct 9, 2004)

I was under the impression that PAR meters measured only light that was photosynthetically available, and it was LUX meters that have the shortcoming you suggested?

Hoppy was doing allot of work on this topic, and he concluded that even high light tanks fall short of that number. If memory serves 15-30 was low light, 30-50 is Med light, and 50+ is high light. I've seen Tom say 40-50 is a good starting point for most people, and I've also seen very high light tanks measuring 150+.

All these readings are taken at the substrate BTW - right by the light the readings will of course be much higher.

I had my tank at 30,.. and I had trouble with some plants, I've moved up to an average of closer to 60 now and I'm happier with that.

Whiskey


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## whiskey (Oct 9, 2004)

P.S. my low light tank is much lower of course,.. I run that at 15ish. less in the corners.

Whiskey


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## old 97 (Jul 25, 2011)

I am going out on a limb here and casually disagree entirely with the first response

Here is the skinny
http://www.apogeeinstruments.co.uk/aquarium-par-meters/

real skinny
http://www.apogeeinstruments.co.uk/content/SQ-100_300specs.pdf

This is the PAR #"s people are ( successfully) growing aquarium plants.
http://www.aquaticplantcentral.com/forumapc/dallas-ft-worth-aquatic-plant-club/80982-par-data-collection.html


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## Bryeman (Aug 24, 2009)

I have used the midday and aqua flora lamps with good success before and read on another site that 30-50 at the substrate level should work "in most cases" for carpet plants if everything else is right, so I'll start there once it's time and see how that goes. Thanks for the responses!


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## Michael (Jul 20, 2010)

The Apogee PAR meter is the instrument used for all the measurements in third thread old 97 gave a link to. The spectral response graph for the Apogee can be seen in the second link. No, it is not a perfect match for the spectral preference of plants, but it is pretty close. In practice, a PAR meter gives the hobbyist very usefulgood information from an easy-to-use device.


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## TropTrea (Jan 10, 2014)

whiskey said:


> I was under the impression that PAR meters measured only light that was photosynthetically available, and it was LUX meters that have the shortcoming you suggested?


PAR meters measure all the light as equally as possible across the spectrum from 400 to 700 nm

Lumn meters apply a weighting factor to correspond with the sensitivity of the human eye were green light (not used in photosynthesis) is given a higher multiplier than red and blue lights on the edges of the spectrum.

The draw back is all the meters have some lack of sensitivity on the blue end of the scale. If you have strong blue lighting in the 400nm to 450nm you can end up getting completly different PAR reading between different brands of meters.



whiskey said:


> Hoppy was doing allot of work on this topic, and he concluded that even high light tanks fall short of that number. If memory serves 15-30 was low light, 30-50 is Med light, and 50+ is high light. I've seen Tom say 40-50 is a good starting point for most people, and I've also seen very high light tanks measuring 150+.
> 
> All these readings are taken at the substrate BTW - right by the light the readings will of course be much higher.
> 
> ...


This is why I cannot use my present lights when I convert my 120 gallon tank to a planted aquarium. My present PAR is 215 at the substrate and 420 10 inches from the surface and over 800 at the surface.


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## TropTrea (Jan 10, 2014)

old 97 said:


> I am going out on a limb here and casually disagree entirely with the first response
> real skinny
> http://www.apogeeinstruments.co.uk/content/SQ-100_300specs.pdf
> l[/URL]


If your refeing to my post I will say your link verifies my post. If you look at the graph light starts to be detected less when it is under 450nm and at 450 nm it is only detected at about 50% of its true value. Then when you you look at the red end of the spectrum this meter barely recognizes any light over 650 nm. Now this is one of the brand of meters and if you compare different brands some are much worst than this and some are slightly better.

If there can be an argument is how useful green light is to to the planted tank. Looking at the Photosynthesis protein absorption peaks some will say it it useless. others will argue that point.


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