# What is PAR? And much more.



## niko (Jan 28, 2004)

I found this VERY nice article about PAR. It was fun to read and I even understood what was being said!

I think the club PAR meter should come with a copy of this article 

http://www.inda-gro.com/pdf/aquarium-lighting.pdf

The website is seling a special kind of fluorescent lamps. There is a lot of interesting information on the site - look at the FAQ's first. Since these lights are expensive I don't think this can be considered advertisement. If someone from the club spends $500-$1000 or more on such a lamp I bet the next club meeting will be at their house so everyone can see the beast. Hope this thread doesn't get deleted.

And here's a good write up what is what currently in the world of efficient lighting. Turns out that one of the big LED companies is about to release a super intensive LED - 200 lumens per watt. I am not sure how bright that is but a 54 Watt Giesemann Midday T5HO bulb is 5000 lumens and these things are bright. At 200 lumens/watt these new LED would make 10,000 lumens with 54 watts. This is like using a single 54 watt tube over a 55 gallon tank to grow anything you want. As it is now a 54 watt Midday is medium light over a 55 gallon tank.


----------



## freshyleif (Jan 9, 2008)

Dude Niko that is the best thing I have read on light ever. Thanks for finding. Hope this is made into a sticky for people to use. Like you said very easy to understand.


----------



## Newt (Apr 1, 2004)

PUR is much more meaningful to plants as PAR will include green and yellow which doesn't do much for photosynthesis.


----------



## houseofcards (Feb 16, 2005)

That's definitely a nice article on laying it all out and explaining it without going over the top.

Interesting, the article goes on to describe the three light levels based on PAR as:

Low 40-80
Medium 80-120
High 120+

On TPT in an write up by Hoppy. These levels are:

Low 15-30
Medium 35-50
High 50+

Honestly I don't think any of those levels are built from any real scientific data.


----------



## fishyjoe24 (May 18, 2010)

p.u.r. is what is needed because that is the actual useable light.


----------



## niko (Jan 28, 2004)

houseofcards said:


> That's definitely a nice article on laying it all out and explaining it without going over the top.
> 
> Interesting, the article goes on to describe the three light levels based on PAR as:
> 
> ...


Well, I messaged Hoppy with the intention to ask him exactly questions like that. The LED craze is all fine and dandy but what do the plants think about us feeding them measured wavelengths. I didn't get to talk to Hoppy - didn't get the feeling he wanted to.

Now what Joey is saying about PUR (how much of that PAR you are blasting your plants with is actually Used) makes more sense than making up a neat little table with "low-medium-high" PAR values. I didn't know what PUR is so I found this:
http://marine-engineers.org/par-vs-pur-2/

So what happens here is that PAR is easily measured but PUR depends on the plant. Things get hairy here and not easy to measure. Trying to figure out what plant likes what wavelengths is probably like asking 300 people sitting in a room what is the best room temperature for each one of them right now 

And for the real aficionados here's a headache-causing thread to enjoy:
http://www.plantedtank.net/forums/showthread.php?t=78632&page=4


----------



## houseofcards (Feb 16, 2005)

I'm also confused about the light saturation level experiment mentioned in that piece. According to a Walstad experiment (unless I've misread it) M. brailsense was exposed to between 45 and 2000 umol and the plant didn't increase photosynthesis any further past 200 umol. Drawing the conclusion that anything over 200 was wasted light. What if the plant was deficient at the point? It doesn't say anything about increasing ferts and/or co2.


----------



## Newt (Apr 1, 2004)

I'm not sure I understand what the ultimate goal/objective is here. To grow plants faster, better ????

If you provide your plants with a light source that contains blue and red light and intense enough to adequately reach the bottom of the tank, provide CO2 and ferts - the plants will grow. One photon of blue and one photon of red provide a plant with the same amount of photosynthetic energy.

More important/useful than PAR is a normalized spectral plot of the bulbs output. One of the problems with saying this type bulb is this intense vs this one (as in the attached article and Hoppy's work) is that they didn't try all bulbs in a category and don't take into consideration blue and red emissions separatley from PAR measurements. They probably tested one or 2 and made some conclusions. I have T8 bulbs that output more microeinsteins than T5 bulbs. Not all bulb types are equal. See the attached gif of a normalized spectral plot of 2 T5HO bulbs. If you made some conclusions of T5HO bulbs based on the ATI you would not have an accurate picture for that bulb category.


----------



## fishyjoe24 (May 18, 2010)

think of winter. . Plants use light to turn water and carbon dioxide into oxygen and glucose. Glucose is a kind of sugar. Plants use glucose as food for energy and as a building block for growing. The way plants turn water and carbon dioxide into oxygen and sugar is called photosynthesis.chlorophyll helps make photosynthesis happen. Chlorophyll is what gives plants their green color.

During winter, there is not enough light or water for photosynthesis. The trees will rest, and live off the food they stored during the summer. They begin to shut down their food-making factories. 

So wouldn't to much light, with out enough c02 and ferts. just be waste because they could only make energy so fast.


----------



## Newt (Apr 1, 2004)

Barry James' 'A Fishkeepers Guide to Aquarium Plants' has this info starting on p.20

http://www.amazon.com/Fishkeepers-Guide-Aquarium-Plants-Illustrated/dp/1564651738

If your plants have too little or the wrong type of light they will be pale and have elongated stems between the nodes. Too much light your plants will have a washed out bleached look.


----------



## fishyjoe24 (May 18, 2010)

so I guess that's why my crypts are starting to fad. I have the 27g marine land tank with the led light, I might have to save up and get a t5 light fixture.


----------

