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Re: Test Kits again

> From: STDIXON <stdixon at bechtel_com>
> Subject: Test Kits Again!
> I don't know how much of this problem might be attributable to 35 hours
> without CO2, but I have the feeling I've been running at absurd levels of
> nitrate for a month or two.

	At least that long, I would think.

> Does anyone think the nitrate levels could
> have spiked in just over the two days without CO2?

	No way.  Just work out the mass of KNO3 required to give that
concentration in your tank.

> Maybe the astonishing
> point is that a fairly (otherwise) well-run PMDD set up was able to sustain
> up to 200 mg./l nitrate without self destructing!

	The presence of lots of nitrate is not a great problem in itself,
but is a symptom of problems.

> If I've got this story
> right, I just don't know how a beginner could judge nitrate levels using
> the cheap kits???

	I keep at least one test solution, with a known NO3- concentration,
and run tests on that and on a blank (RO water) from time to time.  If I 
use a 40 ppm (nitrate) solution, and try to keep the tank nitrate at
5 - 10 ppm, then the tests on the reference, the blank and the tank water
should all be clearly different.  Test kits that use solid tablet reagents
should be good for quite a while if kept cool and dry.

> Now for some good news:
> A friend of mine got his Ph.D. in the metabolism of P and K in grapevines. 
> He loaned me a "Horiba compact ion meter" which he uses to measure the K
> ion levels in grapvines (the leaves and soft stem tissue is squeezed
> through a garlic press to make the sample liquid).  This little gadget is
> about the size of two credit cards and costs about $400.  It's available
> from Spectrum Technologies, Inc. Plainfield, IL (800-248-8873).  The
> instructions state that it works on the "ion electrode" method (whatever
> that is).  You put 2-5 drops of sample liquid on a half inch plate with two
> "sensors."  In the 1-100 ppm range, it claims an accuracy of 1 ppm.
	It sounds too good to be true, but I would like to be wrong!
Look out for interferences, i.e., what _else_ does it respond to?  What
else is in grape plant juice?  Presumably those ions don't interfere, if
this device works.  Do the other ions in our aquaria interfere?  Borrow it
and run a few tests with known solutions, including lots with Ca++, Mg++,
NO3-, SO4--, HCO3-, Na+ as well as the K+ you want to measure.  How long
does it last?  If the electrodes die in a few weeks, it would be an
expensive proposition.

Paul Sears        Ottawa, Canada

Finger ap626 at freenet_carleton.ca for PGP public key.