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Re: [APD] watt/gallon rule


Thomas Barr wrote:
>> I never discounted a controlled study, I've done them on lights and can suggest a very easy >>and simple way to do this(see above), not with 600-2000$ or more light meters.

>Without light meters, the study isn't of much use to anyone. 
Well actually it was and is. The issue back then (we had candles to light our tanks.......hehe) was this mumbo about how significant color temps were and how certain spectrums caused algae and some did not but grew plants.
Now in a controlled isolated study, this might be true, the subtle dynamics in the Ocean, large lakes allows certain algae to gain a slight upper hand.
But field studies, labs studies, greenhouse studies and modeling are all very different critters.
Just becuase you isolate something in a controlled and measured manner in the lab, does not mean it applys to an aquarium.
All in all, even in the lab, the measuring of light is tough and very difficult even for feeble minded scientist. 
But I also decided to see what was the upper limits of the light intensity, so I added as many bulbs as would fit (who is going to add more than that?). Then I added PC lights, at the time, 5.5w/gal in a 16" deep tank and mirrored reflector with perhaps 100 species passing through the tank over the years taught me a lot. For one, we needed much more, 2x the prevailing CO2 levels that were recommended at the time(10-15ppm) for this much light.
So once that was addressed, we could go back and assume most folks would not have this much light on their tanks(A fair and safe assumption, and still valid pretty much today). So now we know how much CO2 is needed(which is also supported from the lab experiements on CO2 gas exchange and light saturation values for 3 common submersed aquatic weeds, as well as some anecdotal comments from several folks on the APD when it first started) , how much nutrients are needed.
Now we can proceed.
So that was the upper practical range(notice, I have not discussed units other than w/gal). Now what about the minmum range? I used a 24" deep tank and only added 1" of onyx sand and used a common weed, Pearl grass. I used PC lights again, this time less than 1 w/gal. Plants grew very well.
So now I've explored both ends of the 2-4w/range and have good success, I go and try it on other tanks. I ask other folks if they also have been able to grow Gloss at less than 2 w/gal, most folks back then only had 2w/gal, PC lights were not really avaiable nor cheap back then relative to what many used. I checked out other folks who had low light and were growing these same so called high light plants. The observations concurred with the generalization. 
>How are you 
>proposing to quantify the results of such a study so that the results 
>can be applied to arbitrary bulbs and setups? 
Well, by already knowing the lower and upper ranges, simply by picking a middle range of effective wattage, it appears to work just dandy. 
The issue is one of need and how much variation all the precision will gain you. 
Our tanks are basically light limited and it's the one thing folks really cannot measure easily, nor address like CO2/nutrients. Where you take the light reading matters in the tank, plant species, plant canopy, age of the bulbs, trickier variables than the CO2/nutrient issues.  
Add that to a huge number of bulbs types from all over the planet, well, we are really starting to get way out from a practical study that is "standard". 
>If you do this study using 
>a light kit from AH Supply, how will this knowledge correlate with ODNO 
>setups, or MH?
I've come up with about a 1.5x more light for PC/MH's factor vs NO FL's. You can also use lumens per watt and convert that in PAR/watt. That would be a bit more useful. 
But.............even spread of the light becomes another issue, the same issue is true for MH vs PC/NO FL's.
So where you take that measurement is critical, MH's produce an archery target like intensity pattern. Long PC/NO bulbs produce a linear stretched rectangel version of this pattern. 
There are few standards here. 
That makes things much more complicated.
Now you need to measure where the plant is in relation to the bulbs and also deal with a MH vs PC vs NO, vs VHO, ODNO ad nauseum..........
> You can't do it without measuring. 
Why not?
We have for years using w/gal.
Try it and see.
By telling the bulb age, the type, distance from the bulb, this will give you a fairly close approximation, which is about as close as folks here are ever going to get.
>Measuring is the basis 
>of all empirical knowledge, and without measurement there is no real way 
>to apply the knowledge to a new and unique situation.

Really? Are you sure you want to go with this one?

>If conducted the same study, but measured PAR in some standard way, that 
>instantly makes the results applicable to any bulb for which the PAR 
>ratings are known as long as other variables are the same. That seems 
>much more useful to me.

Well, it would except for all those variable I already mentioned.
Where you would take the PAR readings, distance from the light source, no glass tops, no surface films, similar plant height(reflection issues if plants block the glass reflection or expose it more), you'd have to qualitify a lot of things. By the time you do that, all the accuracy you hoped to gain is now not so accurate to general public's use.
It would take a long time to investigate the differences with each issue 

>This all gets to my original point that there needs to be some sort of 
Yep, I agree with this one, but it's not going to occur since there are so many types of bulbs, light types, tank types/plant layouts etc etc
PAR/Watts for each bulb seems about the best we can hope for.
Or a cheap LiCor meter:-)
> All of this hodge-podge of knowledge and anecdotal 
>experience is making it much more difficult to advance the body of 
>knowledge in this hobby than it needs to be. 
Irony has no limit: your previous statement about discounting knowledge/belittling ideas has gotten you into quite the pickle with the above. 
I greatly value such knowledge and find a great utility in people's observations.
When added with more controlled approaches, these observations can help set up a test to see if it's true or not.
Some anecdotal:
Many suggested high PO4/NO3/Fe etc caused algae.
So I added PO4 => no algae but much better plant growth. So why was algae growing in the first place? No testing, I just kept adding things till the plants no longer have a positive response. I've since obviously done a lot of testing, more than I care to admit. But I gained a lot out of the testing and helped the general public. If I do the work, I want some gain. I'm not so sure I want to get into testing the lighting quagmire. I'm trying to find something useful from doing all that work that folks can use. 
Folks often say specifically of the plants they plan on growing, the light types they are considering for the tank etc, this goes a long way to suggesting a good set up, based solely on anecdotal experiences of folks that have done it successfully with similar systems.
If they have a little one way or the other in terms of PAR intensity is not important as simply having _enough_ PAR intensity. See below for ideas about finding the minmum levels of PAR for submersed aquatic plants.
>This lack of 
>standardization and definitive, quantitative analysis is the whole 
>reason there are prolonged debates about this lighting and that. 
Why not approach it from the back door, focus on CO2/nutrients, things aquarist can measure and address? Even if we had these results, would it change anything significantly for aquarist? Think about that and all those variables folks have tank to tank, plant species to plant species, aquascaping, surface films, glass tops/open tops, distances from the each plant, patterns of light intensity, depths, on and on............. 
That's a lot to account for...........
>doesn't have to be that way. There is a definitive answer on the minimum 
>light required,
 I have given you a min light actual number for Hydrilla, 10-12 micro moles/sec/m^2.  I can give you the citation as well and personally know the researcher who was also a past professor(Dr Bowes, UF) of mine. Now, having said that...... I might know what to address and some of the potential confounding differences between the lab study and the practical aquarist planted tank.
Have you offered up one min light level for any aquatic plant? Lots of talk of empirical knowledge, but no data on plants? I think you might start by first seeing what the minmum levels of light are for as many aquatic plants as you can dig up in the research literature.
> or the most PAR per dollar/watt,
That's already been done(PAR/watt). See previous post link from Daniel's web site. 
The AB HQI's has the best as I recall. But perhaps it could be expanded. 
I'll assume he used new bulbs. and similar distances etc.
Many of the reef sites have bulb and par data. Those folks love to spend money and time:-)
See ReefCentral. The color temps will be different in many cases to our cases, but many folks growing FW weeds also use 10K reef bulbs and they have data for the 6500K, 5000K, 5500K MH ranges typically.
But they have trouble growing a few sps corals and the field data showed they could not add enough light for many species so they went out and crammed as many 400w MH's as they could. The corals grew well and have nice colors even though the intensity was 4 x less than their most powerful light set up in terms of PAR. 
Things do adapt.
Plants do.
See this post:
>and just about any 
>other topic involving a result that can be measured empirically. 
>Just because we don't know the answer yet doesn't mean there isn't one.
>Jerry Baker
My question is more basic.
Why do we need to do this ? Why/how does the w/gal rule not work?
Basic questions might seem too obvious, but I ask them anyway. 
Tom Barr



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