I started a fishless cycle in my RO water (internally filtered) tank on 15th June, bumped with API Quick Start, Prevent Algae, Stress Zyme, Stress Coat (topped up weekly) and using ammonia to 2ppm (later shifted to 1ppm when I realised I'd misread the colour). No plants to date, but two large pieces of bogwood. Artificial sand substrate, so agitated weekly along with the water change.
Started off fine, ammonia from 1ppm to 0ppm in 24 hours, a week so later, the nitrites started to shift, 90% water change when they were over 5ppm for a few days. Had the temp up at 28-30 degrees C after the first week.
pH values between 7 and 7.4 most of the time. Sudden dip to 6.8 a week ago so I added 1/8 tsp of bicarb of soda (know of the downsides but there will be a pre-fish water change) to my 80 litre tank - 98 litre tank with 80 litres of water in, that is (full given the bogwood etc).
Problem: the other half of my household didn't like the filter and bubbling noise so it was turned down from about two weeks ago til a couple of days ago (against my preferences). (In the longer term it is going to be 25% or more planted so hopefully no long term bubble fights.)
This didn't affect things for a while but then my ammonia-eaters slowed down. From cycling 2ppm in 24 hours they went to taking two days or so to clear 1ppm, and after the last ammonia dose three days ago, it took twelve hours to go down to 0.5ppm ammonia and has been stuck there for the last three days (I'm checking every 12 hours). Nitrites have been 0 for weeks but for the last few days I'm not sure if that's because there's little being produced.
Ph is now at 7.8 (KH and GH both between 60ppm and 90ppm). I'm aiming for a 7.0 or 7.2 final pH with temp. 24 degrees for my beginner fishlist.
I'd understand the stalling if my nitrite levels were elevated, but nitrites consistently 0 and nitrates 80ish (API master test kit).
The filter is now up and I've turned the temp down a shade (still over 27 degrees c) - do I just sit and wait for the ammonia eaters to get their stride back, or am I missing an essential action or a fundamental problem?