Test Kits Do Not Agree

I switched to a Hagen Nutrafin test kit with several different tests
in the same kit. It has a test for NO3 which I used to cover using a
Tetra test kit.

I ran tests for NO3 using both kits on samples from the same body of
water. The new (Nutrafin) kit gave me a reading at or below 5 mg/l
while the Tetra kit gave me a reading at or excess of 50 mg/l.

I repeated the tests twice and got the same results.

Apart from the Tetra kit being a year old are there any other reasons
for these results to be so far apart?

n Sun, 15 Feb 2004 01:39:28 GMT, The Kenosha Kid
wrote:

I switched to a Hagen Nutrafin test kit with several different tests
in the same kit. It has a test for NO3 which I used to cover using a
Tetra test kit.

I ran tests for NO3 using both kits on samples from the same body of
water. The new (Nutrafin) kit gave me a reading at or below 5 mg/l
while the Tetra kit gave me a reading at or excess of 50 mg/l.

I repeated the tests twice and got the same results.

Apart from the Tetra kit being a year old are there any other reasons
for these results to be so far apart?


One of my reasons for not doing any regular testing is the variance in
reading between products. Who to believe? I guess the best thing is
stick with one and assume that any movement is real even if the
absolute value is wrong. It would be nice to have a "standard".

My attitude, if the tank looks healthy, take a reading and set that as
the standard for that kit. Then if the tank goes crazy test and
compare to your "standard" to detect if anything has changed.

"Dick" wrote in message
...
n Sun, 15 Feb 2004 01:39:28 GMT, The Kenosha Kid
wrote:

I switched to a Hagen Nutrafin test kit with several different tests
in the same kit. It has a test for NO3 which I used to cover using a
Tetra test kit.

I ran tests for NO3 using both kits on samples from the same body of
water. The new (Nutrafin) kit gave me a reading at or below 5 mg/l
while the Tetra kit gave me a reading at or excess of 50 mg/l.

I repeated the tests twice and got the same results.

Apart from the Tetra kit being a year old are there any other reasons
for these results to be so far apart?


One of my reasons for not doing any regular testing is the variance in
reading between products. Who to believe? I guess the best thing is
stick with one and assume that any movement is real even if the
absolute value is wrong. It would be nice to have a "standard".

My attitude, if the tank looks healthy, take a reading and set that as
the standard for that kit. Then if the tank goes crazy test and
compare to your "standard" to detect if anything has changed.

Excellent advice. Different elements in the water will influence the
reagents as well, so accuracy also depends on what is in your water.
Well water in particular seems to have the greatest variety of stuff,
messing up pH measurements in particular. If you have the patience, you
can experiment using RO water, halving or doubling to see if the test kit
tracks the ratio. Also the light used to view the results will skew
results. I like using a lot of natural light when guessing the levels.
I also believe that in general, women's colour perception is better than
men, so get them to read the chart. Isn't there a joke regarding a
male's colour perception being limited to 16 colours, and peach, lilac,
mauve, violet, (and a bunch of others) are not real colours, but the guys
smile & nod anyways ;~)

NetMax

The Kenosha Kid wrote:

I switched to a Hagen Nutrafin test kit with several different tests
in the same kit. It has a test for NO3 which I used to cover using a
Tetra test kit.

I ran tests for NO3 using both kits on samples from the same body of
water. The new (Nutrafin) kit gave me a reading at or below 5 mg/l
while the Tetra kit gave me a reading at or excess of 50 mg/l.

The Hagen kit is infamous for reading low. The problem is the third
reagent, which you must shake and dispense without allowing particulate
matter to settle. This same particulate matter will often clog the
nozzle, rendering the kit useless. Hagen will replace the third bottle
with a glass bottle, but one wonders why they have been selling this kit
for years with the same problem.

On Sun, 15 Feb 2004 01:39:28 GMT, The Kenosha Kid
wrote:

I switched to a Hagen Nutrafin test kit with several different tests
in the same kit. It has a test for NO3 which I used to cover using a
Tetra test kit.

I ran tests for NO3 using both kits on samples from the same body of
water. The new (Nutrafin) kit gave me a reading at or below 5 mg/l
while the Tetra kit gave me a reading at or excess of 50 mg/l.

I repeated the tests twice and got the same results.

Apart from the Tetra kit being a year old are there any other reasons
for these results to be so far apart?

Update


Last week I made a trip to Dolphin Pet Village with a vial of my water
and had them test it.

Dolphin, using yet another set of reagents, came in at 10 mg/l or
below so it looks like the old Tetra kit is fubar and the Nutrafin kit
with it's reading of 5 mg/l is ok. It suggests that there is a
plus/minus 5 mg/l tolerance on the test.