@Andytheminion Thanks, several points to consider.
The Tetra strip's colour chart for NO
3 has readings for 0, 10, 25 50, 100 & 250mg/L. I'm fairly sure ppm and mg/L are interchangeable. Additionally, 0 through 25 are marked as "Safe" and 100 to 250 as "Water Change". The assumption I draw from this is that 50 is neither safe nor requiring water change, which kind of chimes with
@Sue recommending Tap plus 20ppm which would give me an optimum value of 60ppm.
I can accept that I may have been overfeeding. With the addition of our final 4 Corydoras, I've been experimenting with NovoTabs, as you know from another thread. The water I removed today had plenty of poo in it and I notice now that the whole tank has a slightly brown tinge to it. With the large size "hoover" I've got, it takes a 20% change to give me the time to go over all the substrate twice.
I don't have any distilled water to hand, but I understand the mathematics of diluting samples to bring them in range of the reagents. For now, I have dosed the whole tank with SeaChem Prime in addition to using it for the latest 20% refill for Chlorine/Chloramine as it's supposed to also "detoxify Ammonia, Nitrite and Nitrate, allowing the biofilter to more efficiently remove them". Bit of an odd statement in SeaChem's sales blurb as, as far as I'm aware, the biofilter only deals with Ammonia and Nitrite which is why we need water changes and/or plants to handle the Nitrate.
We're now at our desired stock level and the Community Creator is telling me we're at 79%.
As recommended I'll do daily changes until I get a handle on this, as well as reducing the feeding.
@fcfm My experience to-date has been similar in that I use Tetra strips and MA, where I get our stock from, are fairly consistent using their JBL strips. Up until now I've trusted the Tetra strips after confirmation of liquid-based tests at MA. It's just this blip of why, having done a water change, the high level of NO
3 didn't reduce after the water change that bothers me.
The guesswork involved in reading the strip colour against the scale is a major problem. On 26th Nov, after a 20% change, my NO
3 went from 75 to 35. Both these values obviously guesses as the colour lay between 50 - 100 and 25 - 50 respectively. Similarly, before and after on 2nd Dec (when the Cories were introduced) went from 100 to 50, no guesswork needed as the colours matched up OK.
My best guess at the whole problem is that I've been overfeeding, possibly from sometime after 17th Nov when we introduced 8 Guppies and also experimented with NovoTabs. All causing the NO
3 to spike and the granularity of the test readings is not fine enough so what could have been 100-ish+ before could easily be 95+ now. What liquid-based kit(s) would you recommend to cross-check against the Tetra strips?