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re: For Dupla folks - Duplaplant tablet question
Kelly Beard wrote:
> I use RO or DI water for water changes. My usual
> formula is to take the water which is stored in 5 gallon
> jugs, and add the following - 1/4tsp baking soda, 1/2
> tsp RO Right (which I might bump down to 1/4tsp) and 1
> Duplaplant tablet, crushed in a motar/pestle.
> Last week I decided to use my iron test kit (LaMotte). I
> got a small shock when it read .5ppm iron. I wondered
> how this could happen because a previous measurement
> put me right at .1ppm. I thought I was using too much
> Duplaplant drops (4-6 drops daily), but I had a hunch first.
> I mixed up a 5 gallon jug of DI water, crushed up a tablet
> and mixed and let the water sit for a while. I tested the iron
> last night - something like .6ppm iron. Now, I bought the
> 50 count tube of tablets from Pet's Warehouse. It says it
> treats 250 gallons. 250 gallons / 50 tablets = 5 gallons per
> tablet. So, if the magic number is .1ppm iron, then what's the
> deal? Maybe the testkit?
Your experience with dosed concentration of Duplaplant is the same
one which I posted recently. (original message below) The LaMotte
results you site are very similar to results I obtained from a sample tested
using an inductively coupled plasma emission spectrometer. (0.6 mg/L)
as against (0.66 mg/L) My prior observations using LaMotte also always
showed high iron values in the Duplaplant and to this day I only have
questions, not answers. Wouldn't it be nice if a Dupla rep could set
the record straight?
Subject: Dupla Fe, K Test
From: "Christopher Coleman" <christopher.coleman at worldnet_att.net>
Date: Fri, 4 Dec 1998 11:59:06 -0500
I recently submitted the Duplaplant and Duplaplant 24 fertilizers
from the Dupla fertilizer system for testing to the University of Maine
at Orono's analytical lab which is maintained by their department of
Plant, Soil, and Environmental Sciences.
The results were as follows:
Fe: 13.2 mg/L
K: 140.0 mg/L
Fe: 0.455 mg/L
K: 0.042 mg/L
All tests with exception of the Duplaplant24 were performed
using a Plasma AtomComp inductively coupled plasma emission
spectrometer. K testing for Duplaplant24 was performed using a
Thermo Jarrell Ash atomic absorption spectrometer due to its low
2 tablets from two separate lots were diluted in 1L of distilled
water; the solution was than diluted with 1L more of distilled
water to obtain a 1 tablet concentration equivalent.
10 "typical" sized drops were diluted in 1L of distilled water; the
solution was submitted as is for testing and the numbers presented
here adjusted by a factor of 10 to obtain a 1 drop concentration
The recommended rate of dosing into aquaria is 1 Duplaplant tablet per
20L of water change water and 1 Duplaplant24 drop daily per 50L of total
tank water. At those rates, the products would produce iron concentrations
in the tank of 0.66mg/L for Duplaplant tablets and 0.0091 for Duplaplant24
drops. The Duplaplant value seems high and inconsistent with Lamotte test
I note that an earlier post in the Krib also performed Fe and K
testing on Duplaplant tablets. While the sampling than was done
using an unreported amount of distilled water, the proportion of
iron to potassium then (Fe=234 mg/L, K=2480 mg/L ) and now
is highly consistent. This leads to speculation on the value of
extrapolating the remaining parameters measured in the earlier
test to obtain values when diluted in 1L of water.
Finally, before submission, the Duplaplant24 sample was also
tested for iron using Lamotte test kit model P-62. ( 0.2 accuracy in the
range of 0.05 - 1.0 ) The results were 0.11 mg/L or a deviation
from the spectrometer's results by a factor of more than two (2).
Is this is acceptable at the very low concentrations involved?
christopher.coleman at worldnet_att.net