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

[David Aiken <daiken at iprimus_com.au>]

On 19/09/2005, at 3:14 PM, Jerry Baker wrote, with lots of cuts:

> You don't need a measuring device to make measurements. Devices  
> just aide our senses where we do not have the ability to resolve  
> the detail we seek. You do not need a ruler to see that a tree is  
> taller than grass, but you probably need a ruler to see that US  
> letter-sized paper is slightly wider than A4 without holding them  
> next to each other.

> No, it isn't. I think you are just thinking of measurements as  
> always being conducted with a device.

My dictionary defines measurements in terms of scale and while there  
is a scale in bigger/smaller, and I'll give you that, there is no  
scale in many of the other things I mentioned. Not all knowledge  
relies on measurement, and not all empirical knowledge relies on  
measurement. I do think knowledge relies on observation and I am  
drawing a distinction between observation and measurement. The terms  
are not interchangeable.

> My whole point is that you cannot definitively say which variables  
> matter and which don't unless you do the study. I am truly  
> surprised at how much resistance there is to this idea. Maybe it is  
> true that there are too many variables to account for, but it's  
> also possible that none of those variables you listed have any  
> measurable effect. Have you tested that? If not, why postulate  
> otherwise?

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? 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.

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.

>> And the real trigger for me in your post was your claim about   
>> measurement and empirical knowledge. I really couldn't let that  
>> one  go past - it simply pressed one of my buttons, and that's my  
>> problem  rather than yours. Your problem is being forced to read a  
>> post as  long as this  :-)
>>
>
> That scares me. I can't tell if you have "art school syndrome" or  
> if it's something else. If you don't know, art school syndrome is a  
> somewhat common affliction where there is a pathological opposition  
> to the idea that something beautiful can be explained, or quantified.

I don't know what you mean by 'art school syndrome'. My undergraduate  
degree is an arts degree in psychology and philosophy. My post  
graduate qualification is in occupational health and safety so I have  
a bit of formal education in some of the life sciences as well as a  
bit of chemistry and physics. I like science and my reading on the  
aquarium front has included limnology texts and material like Adey  
and Loveland's "Dynamic Aquaria", both of which are strongly  
scientific in the measurement sense. I appreciate and value that, and  
I really do appreciate what science reveals. I don't think what  
science does is to explain or quantify the beautiful, but I do think  
that much scientific knowledge is beautiful in it's own right, and I  
do think that the scientific account adds to our understanding and  
appreciation of what is beautiful in something like a planted tank.

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.

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.

As I said above, precision is fine when it's necessary or useful and  
I simply can't see that a really high degree of precision is useful  
here. The general rules of thumb seem to work pretty well and  
encourage people to experiment and control things like fertiliser  
dosage which they are capable of measuring and controlling relatively  
precisely with a lot more ease and much more economically than  
setting up a precisely controlled illumination level. There is an  
element of cost/benefit assessment that we all do and we all tend to  
put our efforts into what will give us the sort of result we're  
looking for with no more cost and difficulty than we're prepared to  
put up with.

I accept that different people will want to achieve different things  
and will see the cost/benefit equation differently. You obviously  
like a high degree of precision and that's fine, but it also isn't  
what most people want in how they run their tanks. What that means is  
that if you want answers to the degree of precision you are  
espousing, you're going to have to do the research yourself because  
it's unlikely that anyone is going to be able to answer your  
question. And I'm not saying that there won't be some people,  
including me, who wouldn't appreciate seeing your results and reading  
about your experiences in obtaining them, but I am saying that very  
few of those of us who would appreciate those results will find that  
the degree of precision they are couched in adds something  
significant to the way we utilise those results in our own tanks and  
I don't think that the level of precision that the results from a  
particular study give you will necessarily make things any easier for  
you when you set up a different tank with different plants.

David Aiken


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