Lighting: Calculating PUR

[Left C]

Thanks for the links, but my fixture fails on both counts. It's a 4x96w SQ pin fixture.

I'm sorry Gold.

For some reason I thought that you have a 4x65w Freshwater Aqualight. That's why I mentioned the GE bulbs.

This doesn't have anything with calculating PUR. I believe that mentioned that you don't like to look of having all 6700K bulbs. Have you tried the Coralife square pin 96w Colormax/6700K bulbs?

I have a fixture with one Colormax/6700K bulb and one Current dual daylight 6700K/10,000K bulb. I like the look. There's highlighted reds, a nice green touch with a little brightness.

With this combo, I have:
½ Colormax bulb
2x ½ 6700K bulbs
½ 10,000K bulb

 

[Crazy Loaches]

Yeah thats a nice thing about PC's you can get two colors in one. I do similar (with 65's) with the colormax/6700K but my second bulb is 10,000k/actinic. I like the look of all 4 colors and I dont mind the actinic either, like a little bit of blue. I'd be pushing it a bit with another 6700K (algae-wise).

 

[ILuvMyGoldBarb]

I've actually thought of that exact combo Loaches. I've looked at those colormax/6700s but I didn't know much about them at the time but the more I've learned the better they seem like they'd be. Since my fixture is a 4 bulb fixture I want to keep my lighting even so I was thinking I could put 2 10,000K/actintic bulbs in the back with the actintic side toward the back of the tank and 2 colormax.6700K bulbs in the front. I'll probably do that the next time I buy bulbs.

 

[Tom Barr]

Ah yes, that should work! But does such an optical filter exist that would be readily available to hobbyist? If your doing the conversion digitally then you need a meter that will take an entire spectral analysis - something thats probably out of reach for 99.99% of hobbyists. I've linked that aqua botanic light comparison many times, its a great source of info. But I question some of the data... like "I used only spectral curves and bulb data I was able to get from the web"... hmmm. And the bulb list there is a bit old.

Overall though, the main difference I see between PAR and PUR is that light in the green range isnt usefull much to plants so it can inflate PAR figures. But green still is usefull, it makes plants really 'glow'.

Well, for a lot less hassle and accuracy, a Apogee light meter measuring PAR is available for about 249$ water proof, good reviews from the Marine folks , myself, and most folks.

You can measure anywhere in the tank and at any distance from the lamps, angle etc.

You can measure the differences between say the top of one plant and that of another nearby.

You can see how low you can go for lighting foreground plants.
You can answer all sorts of interesting questions and have a good base line to compare the other parameters to and how they relate to light.

Unlike KH test, NO3 test kits etc, this is a simple easy to read and use meter.

Regards,
Tom Barr

 

[Tom Barr]

True, its just that I without the knowledge of PAR/PUR-calculations wouldn't have figured out that the wpg-rule can be a bit misleading sometimes and also never gotten any feel for how little PAR/PUR we actually got in most setups. It is quite enlightening to dwelve into the details, and also fun.

But I agree, it's not needed in most cases to run a nice planted tank =)

I think it's odd that so many associate me with not using test kits, yet I test and have more test equipment than any hobbyists perhaps in the world.

Irony has no limit.

But why I use use test kits, meters is quite different from most.
I seek answers to hypothesis that interest me and then set about trying to answer them or rule out things that they are not.

Most just use them to monitor or balance their tank.

While no one needs a test kit, few get into the hobby to test water.
I've yet to meet a person that's said so at least

But we can also say that adding CO2 is not needed either.


I sytarted out never testing, then tested like mad to see why things worked for me and not other folks.

I already knew how to produce and maintain a control algae free healthy fast growing planted tank. Then I got the test kits out.

I measured successes, not problems.
Ooooo..........again, quite a different approach, as most break out test kits only when they have problems............

I'm the other way around.

If you don't/are not able to produce a success or a control tank that's healthy and algae free, as is often the case, then you cannot compare anything, you have no control the gauge anything against.

Now with lighting, that is really what folks are up against unless they go to the PAR light meters.

Measuring and modeling light is very tough.

It drives everything in our tanks and we must have a fair standard to compare it to for the plants, not our eyes, watts etc etc when we talk about it and then discuss how it drives CO2/nutrient uptakes etc.

10% off is a lot here, that can mean BBA, BGA etc.

Still, many will justify and cheapo 10$ NO3 test kit vs a 249$ light meter and try to make rational judgements as best we can.

Still, most are simply tinkering with nutrients/CO2, not really testing critically.
But that is not their goal, they are just trying to do what they believe is best for their tank, plants, fish etc.

But belief and fact are two very different standards.
Something I often get into debates and rants about.

I'm not big on belief however...........

Regards,
Tom Barr

 

[defdac]

After seeing the Apogees sensitivity-range, http://www.apogeeinstruments.com/pdf_files/DRM.pdf
I'm fairly sure I can make my calculator a better and cheaper tool for all aquarists. A bit like EI. =)

So I'm with you here Tom. I've spent so much time upping my knowledge about light, and also have the power to infuse all that knowledge in a simple free tool for all aquarists.

 

[Tom Barr]

Yes, they make some decent items.
I think given the light variables with aquaists, they are massive, it's hard to say much.

LiCOR meters are better, but they cost 3-5X as much.

Regards,
Tom Barr

 

[Crazy Loaches]

After seeing the Apogees sensitivity-range, http://www.apogeeinstruments.com/pdf_files/DRM.pdf.

After seeing that myself, I'm a bit curious. I've seen lights measured in PPFD (mostly Sanjay Joshi's spectral plots for MH) and I always assumed that what it was measuring is PAR... i.e. unweighted energy from 400-700nm. But the first chart on thaty link definately looks weighted, heavily in favor of the red end of the spectrum? Furhtermore there is no dip in the green range where most plants will not abosrb said light. Just a little confused about how the spectrum that meter is weighted corresponds to usefull light for our plants.

And assuming the PPF of that meter is the same measuremnt as Sanjay's PPFD ratings... do you all know that the highest PPFD of any 175W MH bulb is the 15,000K Iwasaki (at least of the many he tested)? And that bulb was nearly as high/higher than many 250W'ers. If PPFD is really a good reading for plants I've been toying with the idea of trying this bulb out, as I have a 150XH tank (4x2x32") that I am thinking about having 1 MH in the middle and a couple 55W cf's front to back on each side of it. That would get the nice crisp white with a little blue that folks seem to like... not that I am bent out of shape about the 'yellowish' low K bulbs... I mean the other bulb I am considering is HPS!

 

[defdac]

But the first chart on thaty link definately looks weighted, heavily in favor of the red end of the spectrum?

Yepp! But also it cuts quite a bit of the red portion 650-700nm which can't be good.

Furhtermore there is no dip in the green range where most plants will not abosrb said light.

PAR measures the green light too, so a PAR-meter should not have a dip in the green portion.

If PPFD is really a good reading for plants

Yes but PAR PPFD is only a little better than Lux. Remember that PAR contains Lux so a bulb with high Lux will have high PAR - but not high PUR since yellow light is penalized in the PUR-measure.