Mr. Barr,
I gather that you believe most test kits are a complete waste of time however I'll have to admit that I like to know the levels in my tank, especially the NO3 since I run a high light tank and dose such large quantities. I also want to study whether there are any long term ill effects of high NO3 on the tank inhabitants such as discus, apistos etc. It seems that the NO3 kits are the least reliable of all but I have seen ads for the Hanna bench testers and ion specific meters. The NO3 meter is priced below $175 US and the 100 tests reagent bottle is priced on the order of $30.

The claims are that this meter uses the "Cadmium Reduction" method but it's not exactly clear to me how this method works and why it is advantageous. I'm aware that most NO3 test kits convert the NO3 to NO2 and that this may be a source of error if the water has an NO2 component already present.

Could you (or anyone) explain the "Cadmium Reduction" method of NO3 testing and advise the advantages over the conventional methods for NO3 tests?

Cheers,

So does this system if it indeed uses reduction of NO3- to NO2- in the presence of Cd. And if nitrite levels in a tank will be high enough to interfere with nitrate testing accuracy most of inhabitants would be simply dead as nitrite is toxic to fish and should be at virtually 0 ppm in any established tank.

Regards.

Vladimir.

I've seen these meters, they are good.
For the $ they are worth it for what you wish to do.

Realize that the inorganic NO3, versus the NO3 derived from waste and cycling are two different things.

One takes time and uses O2, the other does not.
When considering tolerances for fish etc, this needs to be considered and ruled out. Many fish ref's are based on organically derived NO3 vs inorganic sources of NO3.

Cd reduction is the standard in water treatment. Save the Cd leftovers and send them back for regeneration(we do this). Absorbic acid is what most test kits use in our hobby.

The accuracy is about 0.1ppm of NO3 using the fixed colorimeter.
Not bad at all vs Lamott at 4.4 ppm or more between some ranges.

If youm get a spect, then you can test all sorts of parameters, not just one, but in the end, these meters are well worth it if you want to be confident.


Regards,
Tom Barr

$175? wow that seems to be quite a bit less than I remember when I was looking at these things. If this unit also measures other parameters depending on the reagent you use it's not a bad deal.

Not to go too off topic, but I'd like to know more about this organic vs inorganic NO3:

- The KNO3 we add to our tanks is inorganic right?
- So the NO3 from KNO3 is less harmful than organic NO3?
- The majority of hobbiest NO3 test kits (including LaMotte) are testing what? Organic NO3? or both?

No they only are pre set for the NO3 test.
They make a multiple colorimeter for about 750$(uses factory pre set wavelengths), I might get one for home.
The spects are complete, eg they can be set for any wavelength over a wide range, typically 300nm to 750 or 1000nm.
They also cost more.

You can buy a cheap used one on ebay and then use the reagents for these others.

I like the colorimeters because I'll liklely only test those parameters with it and it has a data logger so it imports to Excel so I do not have to import the data manually.

Question 1. Yes
Question 2. Yes, DIN is less harmful generally than DON
Question 3. Total Nitrate, all of it is reduced.

If you do large water changes frequently, this fraction is kept very small.

As far as DON and DIN, that's June's BarrReport article. Next month is DOC/POC.

If you read Italian, Aqua planta and Reef Art has two part article I wrote for them and TAG does also. It discusses Nitrogen better than any thing else out there in terms of aquatic plant hobbyists.

Regards,
Tom Barr

I guess I'm still not clear on the process of Cd Reduction or on how this chemical reaction is different than the chemical reaction occurring with the reagents of the cheapo test kits. Could you elaborate a bit on these reactions? What is so special about Cadmium?

Cheers,