Re:Accuracy, was Hach kits

[Thomas Barr <tcbiii at earthlink_net>]

> I have a slightly different take on the question, "Is this level of
> precision really necessary?" It comes from my background in math & science,
> so I do qualify as something of a geek. The thing is, when you are doing
> calculations involving differing degrees of accuracy, it is the *least*
> accurate measurement which determines the accuracy of the calculation. So,
> if you are concerned with weighing things out to .01g accuracy, or the
> difference between 1/16 and 1/32 of a teaspoon, but do not know how much
> water is in your tank to any more accurate than a gallon, you are,
> technically speaking, wasting your accuracy.
> 
> -Rachel

No, I think _estimating_ is likely as accurate as a good test kit. My
plants/tanks cannot tell.

I think "a range" is something to shoot for and is flexible enough but close
measurements are not something to be trusted easily.
Even if I am off with my teaspoon measurement, I can still be within 1ppm of
NO3 is most all cases, you can add some NO3 if there's a lot of Driftwood,
rock and gravel in the tank. Draining the tank all the way down and filling
with a 5 gal bucket instead of a python etc, will tell you the volume of
actual tank water that's there.

One of the biggest errors I believe is with the KH/pH measurements for CO2
determinations. 0.1pH unit often separates folks from less than 15ppm to
20ppm+. The pH varies through out the day in many tanks. I think having
above 20 by estimations reduces the likely hood of less than 15ppm when you
add testing error in the measurement. Folks are a bit scared of higher CO2
levels but it's not an issue unless you get above 35ppm etc.

But there are ways around spending $ on kits.

I'm not endorsing not testing or not using good kits.....
It's better that not doing it and you can gain some observable insight into
what might be happening in the tank. That interest some folks.
  
Kits are/were invaluable for finding out a number of things that make plant
tanks grow quite well today rather than so damn much guessing like in the
past(and still yet today).

Regards, 
Tom Barr