Hi all,
Nitrate tests
I know
@alto is a scientist, and I would be quite happy that the NO3 levels he records are accurate, but I'm also convinced that there are problems with nitrate measurement, and that many people won't have followed, or fully under-stood the method (shaking with API kits, the need to acidify very hard water etc), and that their values will be much less accurate.
If you live in the UK you can get maximum, minimum and mean nitrate levels for your tap water from your water supplier, and by testing your tap water it should give you some idea of the accuracy of your test kit.
The main problem with colorimetric methods for nitrate measurement is that nearly all nitrate compounds are soluble, so you have to reduce the NO3 to NO2 before you can get a coloured insoluble nitrite compound that you can measure.
Conductivity and the Duckweed Index
I would approach this from a slightly different angle. If you want to keep soft water fish you can just use conductivity and the health and colour of a floating plant, as an indication of the
<"nutrient status of your water">.
I don't think we will have any disagreement that a conductivity meter can give an accurate and reproducible values over a wide range of different water conditions (from DI water at less than 5 microS, up to seawater at ~53,000 microS).
A low range conductivity meter will be suitable for all freshwater aquariums.
Measurement of conductivity (TDS meters measure conductivity and then use a conversion factor (usually 0.64 to convert to ppm TDS)) doesn't tell you which ions are present, but you know that if you have a low conductivity reading that you don't have many of any ion.
I soft water fish and I just keep the plants growing, via the
<"duckweed index">, and the conductivity level between 80 - 150 microS.
cheers Darrel