Hi all,
the only dry fert i am not including is NO3. do u think i should not trust API test kit suggesting my NO3 constantly at 10-20ppm?
Like the others have said, unfortunately <"n
o, you can't trust the kit">, monovalent anions (like NO3-) are difficult to measure accurately, even with lab. grade analytical kit. The problem is mainly interference from other anions.
The problem really is that you need to draw a distinction between NO3 as the end product of the nitrification of NH3, and NO3 added via the disassociation of a salt like KNO3.
In the first case high NO3 levels (~30ppm NO3) indicate that there have been high levels of NH3 and NO2, both of which are toxic to fish. Nitrate (NO3) is the "smoking gun", but it isn't the bullet.
If you add via a salt it isn't toxic until it builds up to high levels, there are values from aquaculture industry where we are looking at long term exposure to <"
200ppm NO3">, via the addition of NaNO3.
If you have a floating or emergent plant? it has access to aerial CO2 at ~400ppm, which means that any yellowing or lack of growth relates to PAR and nutrients, rather than CO2 availability.
I used the <"
aerial advantage"> for the low tech. <"
Duckweed Index">, but you can use plant growth and leaf colour in high tech situations.
cheers Darrel