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Test Kits Again!
To: aquatic-plants at actwin_com
Subject: Test Kits Again!
From: STDIXON <stdixon at bechtel_com>
Date: Tue, 11 Mar 1997 11:48:59 -0500 (EST)
Mr-Received: by mta SFMW.MUAS; Relayed; Tue, 11 Mar 1997 11:48:59 -0500
Mr-Received: by mta SFNSP; Relayed; Tue, 11 Mar 1997 11:48:59 -0500
I feel a little embarrassed to tell this story, but perhaps it will help
I've been working with the PMDD ideas for the past 4 months with lovely
results in a 125 gal. heavily planted tank. (Prior to that, I spent 2
years trying to learn how to "starve" a planted aquarium into good health.
Obviously, I'm a slow learner ;-).
When I first started with PMDD, I continually got zero nitrate readings
with several of the cheap test kits. I think I fooled around with Sera,
Tetra and Red Sea nitrate kits. I was adding as much as 1 tsp. of KNO3 per
day and still getting zero nitrate readings. I imagined that the K2SO4
(provided in about a 2:1 ratio to KNO3) was providing the K needed for the
plants to use the nitrates and thus, drive the nitrate levels to zero.
Paul Sears suggested further nitrate testing to be sure the kit I was using
was working. I bought the SeaChem nitrate test and WALLAH! it had a
reference solution (10 mg./l) and repeated tests clearly showed the
presence of nitrates in my tank. I "read" levels in the 2-5 mg./l range.
So I was fat, dumb and happy, as far as nitrates go.
Last week while I was in Brazil (no, I wasn't able to grab a bucket of that
beautiful laterite soil) two things happened: My CO2 bottle ran out (I
arrived home within 35 hours of the event) and a lot of hair algae started
growing from the gravel. In addition to the hair algae, there was more
green algae on the glass, wood and rocks than I had ever seen (since using
PMDD) and quite a bit of that green algae had a nasty, crusty look to it.
It wasn't the soft green algae that I'm starting to get comfortable with
here and there. A bit of cyanobacteria which had been receding was clearly
advancing again. Other than the first signs of the beginning of crypt
meltdown, the plants looked okay, but I knew something was wrong.
So I started running tests: Hach phosphate test (PO-19) showed just a
trace. Iron levels (Lamotte) were low, but present. No amonia or
nitrites. Replacement of the CO2 bottle brought the pH back down to
6.8-7.0 and the CO2 levels up to 15 mg./l (surprisingly, the fish survived
a pH of 8.0 for a couple of days). Then I opened my new Lamotte low range
nitrate kit and to my astonishment, obtained consistent readings in excess
of 160 mg./l! I used distilled water and RO/DI water (in several different
tests) to dilute the sample aquarium water 1:4 and still obtained readings
off the chart! (I took the nitrate-nitrogen readings (NO3-N) and
multiplied by 4.4 to obtain nitrate levels (NO3) which is what we care
about, right?) This same water "read" only about 10 mg./l on the SeaChem
Following a 75% water change (with the new water testing zero for
nitrates), I'm still over 50 mg./l (again, nitrate not nitrate-nitrogen,
right?)! I'll keep doing daily water changes until the nitrate is under
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. Does anyone think the nitrate levels could
have spiked in just over the two days without CO2? 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! If I've got this story
right, I just don't know how a beginner could judge nitrate levels using
the cheap kits???
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.
I know a lot of us are interested in K levels in our PMDD tanks and how to
"tweak" the PMDD for K. For the good of the order, I would be willing to
put this little gadget to use in any experiments that you smart guys out
there think would be helpful. Any ideas?
Regards, Steve Dixon