Hi Tom,

I've never disagreed with you before but I have to disagree with you in
respect of the Tetra kits.

They're cheap, yes - but in my experience they are accurate enough.

For you, not for me.
I want a test that can measure 0-10ppm ranges and be able to tell
1-2ppm or so differences. I have a lab where we do very precise
testing and water analysis.
I tested the Tetra test some years ago, and others, but for
consistancy, the Hach and Lamott have been far better IME/IMO. I am
not alone on this either. A number of people test their kits and found
a wide range. Maybe your kit is good and maybe that reslution is
useful for you.

I don't know, but reports vary a lot about the accuracy of the cheaper
test kits. I have not heard of these issues with the Hach or Lamott
kits and found them to match the standards with PO4 and NO3.

Even if it is off, you can still sometimes adjust the scale to match
the standards.

Regards,
Tom Barr

I asked a friend of my who is a clinical pharmacologist to test the accuracy
and she told me it was within the resolution. In other words, if the color
of the test says 10ppm and the next higher and lower tests were 5 ppm and 20
ppm she said in her tests the color was accurate for 10ppm.

After reading your post, I performed my own test. I created a solution of
3 teaspoons of KNO3 in 500 ml of water. I then diluted that as 1ml solution
in 1000 ml of water which should result in 20 ppm nitrate.

I asked my wife to then judge the color against the Tetra color chart and
she said 20 without any input on my part.

Maybe the tetra test sold here in Australia is different to the one in North
America?

In any case it seems accurate enough for me :-)


Graham.


Lamott test kits are one of the few worth while kits out there. Cost a
lot more, but if you want something that actually measures the levels
in a meaningful way, then it's worth it.
Cheap NO3 and PO4 kits are, well, cheap. If you need to see if there's
presence or absense, they are not really good there either.

Seeing if a kit is any good is not too complicated, make a known
solution with the weight of KNO3 to a known volume of water, then you
can figure out how much NO3 is in there.

Lamott held up well, I have not found others that do well in the
ranges folks need for planted tanks, many times people think they have
enough NO3 bwecause the kit reads 15ppm or something, when they are
really at 0.0ppm and this can cause algae indirectly and other issues.

Regards,
Tom Barr