Hi, I'm new here and was wondering if anyone could help me with a couple of things. I started a planted tropical freshwater tank about 3-4 weeks ago. I've been fishless cycling without any added bacteria and noticed the first nitrite drop today after 23 days, from about 4 ppm to 0.5 ppm. This was nice to see but I also got a nitrate drop as well (a little over 40 to 20) which doesn't make a lot of sense to me.
I'm using the NT Labs freshwater test kit. Could the nitrate drop be something to do with the way the test works? I read somewhere that home nitrate testing isn't particularly accurate. The results seem to be fairly consistent but that doesn't mean the test isn't just fairly inaccurate. I ran both nitrite and nitrate twice to be sure I hadn't messed the test up.
I've also noticed if I follow the ammonia dosing calculator on this site, and then retest for ammonia, I don't get the expected reading. I think initially I was overdosing ammonia (Dr Tims) and I ended up needing about a dozen water changes to get the nitrites and nitrates back on the measurable scale. Is the lower than expected ammonia reading maybe caused by the added dechlorinator, since I was water changing so much?
Hopefully nitrites continue to drop and it will be interesting to see what happens with the nitrates going forward. Maybe I should buy a different brands nitrate test for comparison?
The other thing I was wondering about is the increase in pH over time. I'm guessing this is something to do with the plants and CO2. I've also noticed my floating Riccia Fluitans (floating crystalwort) starts sinking a few days after water changes. I bought an air stone that can operate on battery for power cuts and just adding it to the tank for about 10 mins and the crystalwort started floating again. Does this mean I need to add CO2? Or oxygen? I'm fairly clueless about plants. I just know not to give them too much fertiliser and light.
The apparent nitrate drop was probably not real - during the time that nitrite was high it would possibly interfere with the nitrate test and give a false high reading so when nitrite dropped and the nitrate test became more accurate again it would appear to have dropped too.
The most likely cause of a rise in pH over time is that something in the tank is releasing minerals into the water - rocks for example.