nitrate tests convert Nitrate to nitrite and then couple to dye for color...
Day 2 you only had 18ppm Nitrate...(20-2 = 18)
so there is that.
Can't tell you why you went from 18 to zero in a day though...
Do suspect you stalled w/ not enough ammonia to keep the chain going..........
Tank doesn't smell rotten eggy?
As a long shot you might have some anaerobic pockets.. How deep is your soil?
That would convert Nitrate to Nitrogen gas...
Really..really.. long shot..
No, I don't think the cycle stalls, it only goes about 24 hours without ammonia as it converts the remaining nitrIte into nitrAte, and when I add ammonia back in, it gobbles it up without pause.
Substrate varies from roughly 3" to 1" in depth.
Interesting. Have you replicated these results many times over the cycle?
Could there be interference in the test kit with something in the water??
I replicate it EVERY time I dose ammonia. So basically every 2 days. (BTW I was wrong on what day of the cycle I was on, I'm on day 14 now, not day 9).
Since most logical explanations have been covered and found wanting, it's time to revisit the assumptions we are working with. First assumption I'd look at is:
No I am not doing the NitrAte test incorrectly, no there is nothing wrong with the test fluid (I have another tank that I test at the same time with the same kit, and it shows NitrAtes in that established, unplanted tank). Using an API Master Kit for my tests. No water changes are being performed that would skew test results.
The API NO3 test is notoriously finicky. Have you done the "calibration
" with it yet?
I haven't done a calibration, but my point from what you quoted in your post was that I show NO3 in my 24 hour test (after ammonia dosing, but not in my 48 hour test, in addition to showing NO3 in a test performed the same day, 2 minutes apart, from a different tank (with no plants). I read that sometimes you have to shake the test solutions because of settling issues, so I've tried that and received the same results. NO3 in tank 1, none in tank 2, no matter what I do, like clockwork. That's what has me so confused, because the test solution would have to be off by at least 10ppm, to show 10ppm in tank 1, but 0ppm in tank 2. But it can't be coincidence that every 2 days the test solution decides to be wonky and suddenly not work right?
Can water chemistry affect the test? I use treated tap water in tank 1 (8.0pH, 10°GH, 6°KH), but remineralized RO in tank 2 (7.4pH, 7°GH, 5°KH).
Im learning as a newb to the hobby but what I have definitely learned ,is that with the API NO3 test it mandatory to shake the living daylights out of " Test Solution # 2". Even go as far as to tap it on a solid surface to disrupt the solution.
I've tried this method too, after the first time I showed a goose egg on 40ppm disappearing in 24 hours. I searched high and low on the internet, and I figured solution #2 "settling out" was the best guess I had. But shaking the solution has zero effect on wether or not I see NO3 in my water. It's a head scratcher for sure. I think I'm going to do a strip test as well as the API test to do a comparison. I dosed with ammonia yesterday at about 4:00pm PST, so I will do my 24 hour test in 5.5 hours but also do a strip test at the same time and post my results.
Update, both API and Tetra Strip test:
Both tests are in perfect agreement on all levels. 24 hours after dosing to 2ppm ammonia. I started with 0ppm ammonia, 0ppm NO2, 5ppm NO3 before I dosed yesterday. Today's readings (on both API and strip test) were 0ppm ammonia, 0.75-1ppm NO2, 40ppm NO3. I will test with both in another 24 hours to confirm levels of NO3 being consumed. Keep in mind that there is still some NO2 that needs to be converted, so add that to the NO3 I will be testing for tomorrow.