Kessil

PAR Readings

[quote author=Gomer link=topic=3963.msg47232#msg47232 date=1214422994]
no need for him to come out when his entire talk is online ;)
[/quote]

That wasn't his entire talk ;)

[quote author=Gomer link=topic=3963.msg47233#msg47233 date=1214423022]
What is the linear velocity of the water in Bali?
[/quote]

Like I said, ask the pro's that question. I can tell you it depends on the reef, just like any place else on the planet. A reef on a point will of course have much higher over all linear velocity, just like a reef situated between two islands where the water is pushed into a smaller area.
 
I am pretty sure his entire talk is online spanning 5 different AA publications
edit:
1: http://www.advancedaquarist.com/2006/6/aafeature2
2: http://www.advancedaquarist.com/2006/8/aafeature/view
3: http://www.advancedaquarist.com/2006/9/aafeature2/view
4: http://www.advancedaquarist.com/2006/11/aafeature/view
5: http://www.advancedaquarist.com/2007/1/aafeature/view

and vortech has a max flow rating of 3000 ghp. The output of the vortech is 3"

The face felocity:

3000g * (231 cu in/g) =693 000 cu in

--> a cylinder 3" x 98089" (or 18.6miles)
--> face velocity of 18.6 mph

The face velocity out of a powerhead is much higher.
 
I did pull this up while googling a little

http://www.balidives.com/dive_sites.htm
Current : Can be extremely strong, more than 5 knots

5 knots is ~ 5.8mph

PS, don't let my OCD get the better of you :p
 
My quality vs. quantity comment I thought was more in respect to his comments regarding "turnover" vs. good flow and ability for the corals to respirate. That is it is not so much how much you have but how it is being generated. Something along the line that you could actually have a bunch of pumps etc that were cancelling each other out.
 
That is his whole hoopla on turbulent vs laminar flow. You have 2 goals with flow. 1) gas exchange from coral into water. 2) gas exchange from water with air. Turbulent flow (standing waves and tons of random powerheads) is great at #1, but not that good at #2.
 
[quote author=Gomer link=topic=3963.msg47218#msg47218 date=1214418627]
If someone is down wind of you, and you let out a really bad fart, can the wind blow so fast that the smell starts getting worse instead of dissipating faster?
[/quote]

Yeah if it blows right into your nostrils.

This brings up another question about skimmer dwell time: People say skimming works better with greater dwell time but that is counterintuitive because you would think with more waste being brought to the skimmer it would collect more. Almost like convection where the higher the flow the more heat transfered because of the greater temperature gradient.

Anyhow, to steer the thread back to the topic, what kind of PAR do reefs get? What are you guys getting in your tank. I'll post before and after pics of my corals as soon as I get a chance.
 
Sure back to PAR.... One reason to stick with using the Electronic setting is, well, it's kinda of a standard. Did the article state they would read the same? Apogee told me they both behaved a bit differently (utilizing different spikes in spectrum IIRC) when I asked years back. Since that was a different email account I don't have it saved, but i'll send another right now :)
 
Well, here's a page out of Apogee's online manual showing the difference in readings between the two calibrations. Of course, I saw this after I bought the meter and had only read the advanced aquarist article where the sunlight calibration matched the much more expense Li-Cor meter. Anyways, measuring PAR in a tank is so subjective with so many variables coming into play that the differences between numbers when comparing bulbs, reflectors, etc., are probably going to be more relevant than the absolute number itself.

I plan to make some grid measurements in my tank to measure PAR at it relates to depth, distance, and angle from the bulb. I'm hoping it will allow me to better plan how I can move corals around in my tank without exposing them to light changes that I can't perceive, as well as develop an idea of what range of PAR values seem to give a particular coral better color, growth, etc.

320183937_pohYn-L.jpg
 
That AAOL article is a bit old since Apogee has since released two if not three upgrades on this model alone (I've had all but the new one..which is coming soon)
 
It also mentions in that chart "Average errors", would it be fair to assuming most metal halide bulbs out there are not the bluer bulbs associated with the aquarium industry? So might be well outside that average?
 
I was wondering the same thing, as I bet these meters are probably designed for use by the agricultural industry, or the "horticultural" industry, and from my understanding most halides used to grow plants are in the lower kelvin range. That said, I don't know if that would change the ability of the meter to assess PAR, since it's only sensitive to light in the 400-700nm range
 
Wow - great service from Apogee. I just contacted them out of curiosity since my order hadn't shipped yet (although it has been two weeks already!) and they're willing to change the calibration for me. Anyways, if you guys ever want to compare meters and see what the different calibrations come up with, esp in our 14-20K bulb range, LMK
 
Boy oh boy, what are your par readings :D


Energy comes in a larger variety of forms on the ocean, than in our tanks. IMO you cannot quantify one against the other, I mean you can try I guess......
 
Nah - I wasn't suggesting a PAR p*ssing contest (is that what you meant?) :D

I just was curious what the difference really would be between meter calibrations. Does it matter - no, but just curious, esp since whenever a new bulb or reflector comes out, there's a lot of data that gets thrown out on RC.
 
[quote author=vapormd link=topic=3963.msg47312#msg47312 date=1214490889]
I was wondering the same thing, as I bet these meters are probably designed for use by the agricultural industry, or the "horticultural" industry, and from my understanding most halides used to grow plants are in the lower kelvin range. That said, I don't know if that would change the ability of the meter to assess PAR, since it's only sensitive to light in the 400-700nm range
[/quote]
The problem is they don't read values equally at each wavelength, which is why you need the calibration in the first place, so the "electric" calibration is still a calbiration for the lower kelvin bulbs in agriculture as you suggested, which IIRC is lower than the sun @5800K

If you could get it calibrated for 14-20k bulbs that'd rock for the electric mode, if you have a 10k bulb you might just use sunlight.
 
I'm confused. Why would there be 2 results depending on what calibration source you use? Is the device that non linear over the bandpass? Is it fitting to two different functions? I thought PAR was defined and not "floppy". Perhaps I am just not understanding how things are done. If I calibrate a photo detector at work with a series of standards, I can bring in a different set of standards from another source and they should agree with each other.
 
Direct your confusion to Apogee so they can clear it up for you :) Then tell us :D
 
I just sent them an email :-D


Oh! This is great. I downloaded their manual for their quantum meter which measures PPF (photosynthetic photo flux in umol m-2 s-1). It looks like they sum up all photons from 400-700nm and weight them equally. As far as the meter is concerned 700ppf at 450nm (chlorophyll peak) is the same as 700ppf at 550nm (a chlorophyll valley).

Now pretend you don't know what your light source spectra is (say you are color blind). You hold your meter over 2 LED lights: one 450nm and one 550nm. The 450nm measure 500ppf and the 550nm measures 1000ppf. "man, the 1000ppf light is so much better! I bet it will grow my corals a ton better then the crappy 500ppf light"

Now, the definition of PPF isn't bad, but our usage of it is
 
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