Hi all,
When you add nitrate (NO3-) from a salt like potassium nitrate (KNO3), the <"
nitrate ion itself isn't toxic to fish"> until you get to quite high levels. Have a look at <"
Nitrate tests?"> for a bit more discussion and some references.
If you haven't <"
added NO3"> (either via a salt or in your tap water) it is the <"
smoking gun"> of previous high levels of TAN (ammonia/ammonium (NH3 / NH4+)) and nitrite (NO2-) and they really are toxic at very low levels.
@Edvet, who posted on some of the threads, really is a vet.
I'd agree to some degree, we don't know at what level nitrate becomes a problem for a lot of ornamental fish. I've kept / keep <"
Apistogramma">
, <"Corydoras"> etc. and, personally, I try and keep nutrient levels down, but it is still the same problem of differentiating between NO3- as the product of ammonia oxidation and that from direct addition. The only real way of doing it is to use <"
nitrogen isotope labelled ammonia">, and even labs. have struggled with this.
I look at it another way and I use the leaf colour and health of a floating plant as a proxy for nitrogen level (<"
The scientific background to the "Leaf Colour Chart"">), it works pretty well as long <"
as none of the other essential nutrients is limiting plant growth">.
<"
Floating plants, in particular">, and plants generally, are very efficient at depleting fixed nitrogen levels. I want plants in active growth, because they are the single factor that has the <"
largest effect on maintaining water quality">.
cheers Darrel