I tested Ammonia and Red Sea NO3 tests with thiosulfate (similar to Prime -
some assert that Prime active ingredient turns into thiosulfate) and I found that the tests are very much interfered with by thiosulfate.
I wanted to do some checking before I said this also for sure happens with Prime. It does.
left pic: Red Sea NO3 pro with ~0.7ppm NO3, top is normal, bottom is with 2x Prime.
center pic: Red Sea marine NO2/NO3 test kit, Nitrite test, sample water has ~1ppm ammonia and ~30ppm NO3. Neither without (top) or with (bottom) 2x Prime does it show any false NO2.
right: API ammonia at 5min with 1ppm ammonia, left tube is normal, right tube is with 2x Prime.
These were done 5 min after addition of Prime. I checked again at 45 min and it still interfered with API total ammonia. I do not know how many hours the interference lasts for.
With Prime, cycling tests are unreliable. The strong reducing agent causes a negative interference with total ammonia and NO3 tests, and probably also NO2 tests (because the final step of an NO3 test is an NO2 test), but I have no NO2 samples to demonstrate that with. I didn't have an API NO2 test handy, but given that it zeros out NO3 tests, I don't see how Prime could positively interfere with an NO2 test to show fake NO2.
(I haven't gone through the specifics of that thread to comment on it)