Not me Fran, not in that sense. KH has little to do with minerals needed for fish. GH has in a sense though, another topic. KH is to do with stability of water in aquariums. In nature it is not important due to the massive volume of water and natural buffers such as humic and fulvic acids(yes these acids buffer soft water up) Hence a soft water tap is nothing like soft water in nature.I believe it was you your self that said fish need minerals and things that only KH can fulfill.
I know very well your water has no buffering capacity. But you only need adding soda bicarbonate if the KH is about to drop to zero between water changes.
a TDS rise, a GH rise, a KH drop and a subsequent pH drop is what causes the very common term "pH shock" event or "Old tank syndrome. TDS drop is a positive move and for the most part is very safe as you're returning the water back to a "Quality level" at which point the fish will feel way better. If its going to make you feel better, I have dropped the TDS on a tank with a quarantined baby clown loach by 100ppm at a time with no negative effect whatsoever. That was after a solid salt dosing for ich.I read articles that say if the TDS changes drastically it could shock your fish. So if I change 75% of this tank water I could potentially kill them because the TDS is going to change drastically.
Think of it that way...Let's say you have water riddled with nitrates to the hundreds of ppm. You are afraid to do big water change to reduce the nitrates? So you keep going the way you are for what reason? One either takes the plunge or takes the risks.
As I explained in my previous post, a TDS meter, although an acronym for Total Dissolved Solids, does not measure solids. It measures ions, i.e. conductivity. The detritus in substrate is a contributor only once said detritus dissolves in water due to chemical and biological reactions. The ions in the water column are the final result of all chemical and biological processes in the tank. Hence why is using a TDS meter as a pollution indicator so important, as it gives away the entire picture.There is no debris on it, very little. Not like having gravel that debris can settle into. I do not, nor will I ever, understand why I am having nitrates and TDS issues.