What is stability? I noticed my diffusor wasnt performing anymore, bubbles became too big so less and less CO2 ended up in the water and some plants started to show it. So I replaced it, meaning I had to re-dial in my CO2. I now use even less CO2 to achieve more saturation, but it also means there was another period of fluctuating CO2 (and not enough CO2 before the switch). And now last night, I had to do a major trim of the biggest plant mass again, so again, fluctuating CO2 (less CO2 used). I am keeping a close eye on algae development over the past few days and the coming days, until I feel the stability has returned. I've spotted some green dust algae, but that was already present (doesnt bother me and seems natural), and the GSA that were receding have gained new intensity. I hope they wont spread too much. But it makes me contemplate on the nature of stability and the importance of it, as such a seemingly minor thing as replacing a diffusor can have such impact, especially on a small water mass like this.
I briefly considered inline diffusor, but I find the glass difussor a better match somehow for this tank. It almost feels nostalgic.