Following up on the conversations from 10 days ago, when I did my last 20% weekly water change yesterday, I checked the before and after parameters, just to see what our NO
3 levels were.
Before the change, NO
3 was at 15ppm. After it had gone down to 5ppm, spot on with my earlier remarks. The funny thing is, out-of-the-tap shows as 10ppm.
This is the infuriating thing about this water-keeping lark. If I start of with 100% of the water at 15ppm, take out 20% and replace it with off-the-tap at 10ppm, no way, mathematically, should I get a new reading of 5ppm.
Logically, it should be somewhere between 15ppm and 10ppm, by my calculation, 14ppm.
Now it could be my test kit playing up (NT Labs 2 reagent liquid test) which would be a bit weird since even if it was inaccurate, all these readings taken over the space of about 30 minutes should at least be consistent with each other. Or the granularity of the colour chart showing readings for 0, 2.5, 5, 10, 20, 40 & 80ppm is too coarse for me and Mrs Adenann to tell if the readings we get are 5, 10 or 20. The reading we get of 15ppm is, obviously, a bit of a guess as the reaction colour is darker than 10 and, we think, lighter than 20.
I can't get too upset by all this as, when we first started the tank last November, the 2 x MAs, P@H and 2 x independent LFSs round here all said they use water off the tap and do nothing to it with respect to NO
3. Their take on it is "it is what it is and as long as it stays fairly stable, who cares?". At least two that I know of don't bother with testing customers' NO
3 at all.
@Littlefish , I recall we had discussion around this topic, amongst others, when we first started out as you're on the same water supply as we are. Have you checked your off-the-tap parameters lately, and specifically, what do you see for NO
3?
Does anyone know of a test that would accurately measure the level, say, to the nearest ppm?