I get the impression that many people think lots of water changes create" instability", when just the opposite is true.
If you do a water change with (for example) pH 7.5 tap water and wait a week, or 2 in between (or a month) water changes (depending on tank size and stocking level)
that pH can drop to 6.5 or even 6, and nitrate can rise from 5 ppm directly after the water change, to 20ppm a week later.
Is that stability?
If moderate water changes are performed every other day or every 3rd day, it stands to reason that pH will not drop as far, nitrate will not climb as high, because those parameters will more closely match the tap water parameters.
Isn't that stability?
A stability experiment we can all do, is to measure pH, and nitrate right after a water change, then just before our next normally scheduled water change, test those parameters again.
This is how I developed my current routine.
Not by some, generic aqua-advisor, or YouTuber's platitude, that has little to do with the reality of my situation.
But by what applies to my stocking level, my tap water type, and my goal for the health of my fish.
My tap water has a pH of 8.2, and non-detectable nitrate.
Where I catch my fish, pH is 8.2 and nitrate is also nondetectable. So this is the goal I maintain for my tanks.

Above are the nitrate and pH tests in a river where I catch my fish.
Below the same type tests done on my tank

If you do a water change with (for example) pH 7.5 tap water and wait a week, or 2 in between (or a month) water changes (depending on tank size and stocking level)
that pH can drop to 6.5 or even 6, and nitrate can rise from 5 ppm directly after the water change, to 20ppm a week later.
Is that stability?
If moderate water changes are performed every other day or every 3rd day, it stands to reason that pH will not drop as far, nitrate will not climb as high, because those parameters will more closely match the tap water parameters.
Isn't that stability?
A stability experiment we can all do, is to measure pH, and nitrate right after a water change, then just before our next normally scheduled water change, test those parameters again.
This is how I developed my current routine.
Not by some, generic aqua-advisor, or YouTuber's platitude, that has little to do with the reality of my situation.
But by what applies to my stocking level, my tap water type, and my goal for the health of my fish.
My tap water has a pH of 8.2, and non-detectable nitrate.
Where I catch my fish, pH is 8.2 and nitrate is also nondetectable. So this is the goal I maintain for my tanks.

Above are the nitrate and pH tests in a river where I catch my fish.
Below the same type tests done on my tank
