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Re: [APD] Just how accurate do we need lighting recommendations to be?

David Aiken wrote:
> On 19/09/2005, at 3:14 PM, Jerry Baker wrote, with lots of cuts:
> I'm not arguing that you can't know what variables matter without a  
> study. But studies have been done and there is a lot of research into  
> plant growth and we do know pretty well what variables do count. What  
> I think is at issue is how they apply in an aquarium and, given the  
> variance in aquariums and the different plant/fish populations and  
> management strategies people adopt plus the level of equipment  
> available to most hobbyists for monitoring and regulating things like  
> lighting and nutrient levels, I am seriously asking is the level of  
> precision you're looking for really going to add anything to how we  
> run our tanks?

Who knows? I bet the people who first decided to study why fish always 
seemed to get diseases and die in new tanks did not dream of changing 
the entire hobby with the knowledge of cycling. You never know what you 
will discover and what its impacts will be.

> I don't think that level of precision is necessary for  
> that purpose. The knowledge may be intrinsically useful to you, but  
> knowing precisely what lighting level you need to maintain the  
> internodal spacing of a particular plant within certain closely  
> specified parameters - your example - in a given tank with a given  
> population and maintenance regime is not particularly useful at a  
> practical level for most people, nor for you when you set up a  
> different tank. The level of variation and adjustment required on all  
> parameters in a different tank than the one which yielded the answer  
> is large enough to ensure that a less precise answer is probably  
> going to be just as useful in practical terms for most people.

Again, I don't understand how you just know that without testing it. I'm 
not saying it is, or isn't the case. I am saying that you cannot say, 
"measurement X will have no value because everything else will negate 
its effects" when you haven't even measured any of those variables or 
observed their relationship under controlled conditions.

> And when I say that the level of precision you're looking for isn't  
> useful in running a tank, I'm not saying it isn't useful in  
> conducting a study and producing data for analysis. Conducting a  
> study and running a tank are 2 very different things and a higher  
> degree of precision is invaluable when doing studies. Precision is  
> fine when it's necessary or useful, but it really doesn't add  
> something in every circumstance. I'm saying our tanks are a  
> circumstance where that level of precision doesn't add anything,  
> simply because of the variation in tanks.

How do you know that?

> I don't know what you mean by 'art school syndrome'. My undergraduate  
> degree is an arts degree in psychology and philosophy. 

You don't have it then. You can usually spot the people I refer to 
because they are young, but reject a lot of newer technology. They will 
say things like, "digital pictures are just so cold compared to film." 
Or, they will swear that CDs sound much "harsher" than LPs.

Now, don't get me wrong - if a person is older and says these things, 
that's not "art school syndrome." Older people usually prefer things 
they are familiar with and that's natural.

> I'm just being extremely pragmatic by asking the question about what  
> level of accuracy we need lighting recommendations for plant  
> maintenance to be. That's not suggesting that people shouldn't do  
> very accurate and controlled studies to find things out. What I'm  
> suggesting is that when it comes to the practical application of  
> research findings that are as precise as you appear to want things to  
> be, the level of precision that is helpful in research findings is  
> much finer than is required for practical purposes in most people's  
> tanks.

Of course it's more than is required. I'm not interested in the status 
quo ... everyone's doing that. I'm interested in pushing the boundaries. 
How do you think someone discovered a better way to measure the amount 
of light useful for photosynthesis? They had to ask themselves why some 
lights seemed to be working better than others in growing organisms 
which rely on photosynthesis. They couldn't just "raise or lower" a 
light over a tank and deduce that, in terms of photosynthesis, light 
with a wavelength between 400nm - 700nm is fairly equal. That took 
measurement and control groups. They came up with PAR. Now we have a 
tool to assist us in further study. One step at a time, new knowledge is 
built on older knowledge.

> And I'm also suggesting that if you want to conduct research to  
> define lighting levels for purposes as limited as controlling  
> internodal spacing in a particular species, the results are going to  
> be so precise that they won't be directly applicable to a different  
> species, they also won't be all that helpful in telling us what  
> lighting levels are necessary to control other aspects of the  
> appearance of our plants, and I ultimately doubt whether achieving a  
> particular internodal spacing is going to ensure that our plants look  
> any more attractive than if we accepted a little more variation in  
> internodal spacing.

Perhaps there is a lot of research that I am unaware of. Is there 
somewhere I can read about internodal spacing its specificity to a 
particular species? This is exactly the kind of information I'm trying 
to get. I don't understand where you learned that light levels and its 
effects on internodal spacing has no bearing on any other aspect of 
plant appearance. Is this published somewhere publicly accessible?

Jerry Baker
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