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Re: [APD] Aquatic-Plants Digest, Vol 25, Issue 55


Thomas Barr wrote:
>> 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. 

>This comment tells me that there is a breakdown in communication 
It simply keeps the original question on track. 
Something often lost sight of and a question still not answered.
>I am not saying that there is something "wrong" with the 
>watts per gallon rule, nor am I saying that I have all the data I wish 
>to obtain (like the minimum light levels you suggested I should have 
>values for before I make any measurements). What I am saying is, how do 
>you know for certain that the watts per gallon rule is the best rule of 
>thumb in terms of accuracy? 
Well......hehe this is precisely my point, you made it for me actually.
Recall all the empirical evidence you've discussed?
Now what about all that empirical anecdotal comparisons folks have made over the years?
Are they not measurements also? And what did they measure that cuts through all the variables? They used the plant's themselves as the test and measurement.
"Hey Bob? Did that 1.5w/gal 55 gallon tank you did with them thar Tritons work for grow Har Grass?" "Yesssum, they shar did." Now if Bob was able to do it, we should and be able to figure it out. I have enough info to investigate..........
You still have yet to offer this empirical evidence you claim is better. Still all talk, no empirical evidence/anecdotal yeehaw. Say Bob has offered and better solution than you have. And I'm waiting to be proven wrong. The graph maybe useful to correlate PAR to Lumens to W/gal, but most folks still think in terms of w/gal, few aquarist around think in PAR/area. It's not a familiar unit and few folks can measure it directly, perhaps there is an indirect way to get at a generalization, but that's about all you will get. Then it's not as precise. But trying stuff out like this is a hobby for many folks. Been there done that.

>Did somebody do some measurements and 
>determine that lumens per gallon, PAR per gallon, lumens per square 
>inch, or PAR per square inch (just to offer some examples) were inferior 
>measures when compared to watts per gallon? 
My issue with that is..............a newbie will know what a watt is and gallon is and be able to figure that ratio rule out pretty easily, but what about PAR? Lumens, CRI, all these technical units used for lighting? Now their eyes glaze over......... 
Even if I did this, I'd have a large margin of error after doing more work, to the extent that I no longer save anything(time, $, etc). 
>Now, you're going to ask, 
>"who cares?" I do, and we all should. If watts per gallon says I need 
>415 watts over my 135 gallon for growing XYZ plants when I really only 
>needed 300 watts, that's a big dent in my pocket book and not something 
>I call "good enough." Maybe watts per gallon *is* the best rule. My 
>whole point is to ask how do we know it's the best without testing other 
 But folks have done many tanks over many years, if you assume NO light levels, you can know you always have enough light at 2-4w/gal, if you add a fudge factor of about 1.5 for PC/MH's this will allow you to use less.
You are talking about light efficency for growth, what is the min amount.
I said awhile back, you need to maxmize the CO2/nutrients to obtain the most light efficency in a plant.
And I also said that is a better area to focus in if this is your personal goal.
Limiting light is the best thing folks can do to slow growth rates down(but not to the LCP).
And it's something I've played with for sometime. 
You can find the LCP or close using light times, changes in intensity(using a bank of lights and stagger them), raise the height etc.
>And, if we do test other methods, quantitative measurement is 
Okay, "Hey Bob? Did that 1.5w/gal on the 55 with the tritons and reeflectror work for ya?"  
My measurement is now now done. If I have issues with the lighting, then I need to focus on the plant species or the CO2/nutrients since Bob was able to do it with new bulbs.
This means far less variables than the method you are suggesting.
And cost less, less work and produces a nicer tank in the long run.
> Sure, plus or minus ten percent doesn't matter when 
>calculating for the difference between a 29 gallon and a 55 gallon, but 
>what if you're calculating the light needed on your brand new 500+ 
>gallon tank? A ten percent error in light requirements might cost you 
>$150 more dollars in ballast and bulb, and $80 a year in unnecessary 
>electricity usage.
>Jerry Baker

Well if $$ is the issue here, good CO2/nutrients etc, less light(more is not better), using high efficency lights such as HQI's, PC's, T5's etc will go a long way. 
You also just try it and see and make sure the plants are pruned the way you want, appear the way you want, and you can change the light time(oh! there's yet another variable!) or stagger the light pattern(Amano does this as do many folks for a high noon effect) to reduce light usage with higher watts.
This can be tailored and tweaked, just like nutrients and CO2 to each tank's needs/wants.
CO2, NO3 etc have ranges for suggestions, you could pursue more accurate measurement with these as well.............
But to what end? At the end of the day, we want results on the plants themselves, they are the focus of the hobby and overall, the best test kit there is since it's they that we are trying to grow and scape with.
W/gal, PAR/Gal, PAR/area etc as long as it's a flexible range, but as soon as you add felxible range..............now you getting further away from that same precision you'd hope to avoid using W/gal............
Tom Barr

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