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Info on par

Coral reefer

Coral reefer

Past President
BARcard
The speaker at last meeting mentioned using a par meter, got me thinking. I know what par is (generally, I think), but if anybody has a link to some good reading I'd like to do some. Also, anybody have a par meter? What brands are good/available and what is the price range?
 
On a side note, any gueses what the par difference would be between 1 actinic reefbrite +1 white reefbrite (both 48") or two 150 watt hqi? Guessing the reflectors have a large impact with the hqi, so let's assume something nice like lumenarc minis...
 
The PAR meters used for reefers are by Apogee and I think are around $240. there was a group buy a while back and they sold for ~$150. I don't know the difference in PAR between the blue reefbrite vs. white reefbrite, I'd guess white ones are at least 2x and likely 3-4x more PAR but those are just guesses hopefully someone has some actual comparisons w/ data.
 
When Jake did his talk on LEDs he was not sold on the idea of PAR as a light value due to the directional output of LEDs, the PAR was better suited as a measurement for T5s and MH.

If your looking to grow coral, at this point more proven technologies would keep the headaches to a minimum. Don't get me wrong I love LED technology and will be adding some reefbrites to my own tank when I'm finally finished with my canopy, but I'm not quite sold on the whole color/growth aspect of pure LED, especially when running a commercial flat like you're going to be.
 
I would say that directionality and PAR are mutually exclusive from the perspective of PAR meters. I would however buck the current/old wisdom that says a photon is a photon in the PAR bandwidth. 1 PAR from an LED system is not the same as 1 PAR on a MH system IMO/E.
 
Cool discussion!

Jeremy, can you elaborate on what Jake meant (or maybe we could ask Jake) about directionality? I'm confused because the type of reflector used on T5/MH affects the spread of light produced just as much as the optics of an LED.

IME Apogee meters give a pretty skewed picture of the actual light output and read low in the blue range. We use a Li-COR spherical sensor (it picks up light from all angles) for making light measurements--it's pricey but might be fun to bring to a BAR meeting for some comparisons.
 
Gomer said:
I would say that directionality and PAR are mutually exclusive from the perspective of PAR meters. I would however buck the current/old wisdom that says a photon is a photon in the PAR bandwidth. 1 PAR from an LED system is not the same as 1 PAR on a MH system IMO/E.
Click to expand...

Hey Tony,

By "not the same" do you mean "is less than" or "is better than"? ;)
 
Wow, thanks for all the input! For the record I am wanting the reefbrite(s) for my home tank, 4x2x2. The coral flat is out a my brothers, Straight mh and t5 for that sucka.
It would be awesome to be able to compare two par meters (especially since I've never even seen or used one!
 
Matt, from what I gather from various threads and from people "of weight", anything within the PAR bandwidth (400-700) nm ultimately behave the same with coral. We normally think of the photosynthetic curve with respect to chlorophyll, but various pigments, cofactors etc make other wavelenths photosynthetically accessible.

My intuition from what i have read on the subjects coupled with first hand experience with MH, T5HO, PC and LED seems to suggest that for a given PAR with an LED setup, you will get different results with a traditional reef light setup of equivalent PAR. It seems (again imo/e) that although there is the potential to grow coral well, the results are different (growth rates/coloration etc). LEDs can easily bleach out corals with far less "power" then MH/T5 (imo/e), but the spectrum REALLY matters(especially with SPS). I don't think that pumping up the blue to compensate the kelvin temp of the white is the best way of doing things. Yes, you can dial in your color, but I think we are really hurting ourselves with both the excessive yellow/green and lack of violet. This is going to sound odd, but right now, I think the LED solution is to mix the usual W/B LED mix and then toss in some super actinic T5HO (or better yet, 420 HVO).
 
I'm not normalizing anything except the abnormal :p

The true PAR normalization is to set int(400,700) F(L) dL = 1 for both spectra.
 
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