Possible stressors that I can think about:
- fluctuating levels of CO2, including a period with over 110 ppm (short - hours, or a day at most); I was experimenting, reading stuff on the net...
- our living room temperature used to be around 26⁰C; when we set up the shrimp tank we decided to lower it to 24⁰ - and we started the regime I described in my previous message; I estimate that, on average, the temperature dropped around 1.5⁰C
- as a long time stressor I can think of increased bioload - I used to have 5 cories and 6 otos in the tank, i.e. around 1 cm fish/liter. For a couple of weeks or so I even had two bettas and 6 Cambarellus patzcuarensis on top of everything else. My Staghorn problems went away after I removed the otos among other things.
I can't think of anything else right now but with
- me being a noob
- the tap water quality perhaps fluctuating,
something else could have happened of course.