Is high TDS related to high Phosphates? I notice my older tanks have high Phosphates 10+ PPM and Cal/mag hardness of about 71 PPM (PH7.4) while my untreated tap water has almost 0 phosphates and 606 PPM of Cal/Mag hardness, KH 143, PH 8. My inside house and aqua source water is now softener treated using potassium and comes out 143 KH and 36 PPM Cal/Mag, KH 143 (unchanged), PH 7.8. Since I have switched to softened water ( I like to use the word filtered) although my fish are generally healthier (fin rot much less prevalent), I notice they get stress if my water changes exceed 30%.
I recently lost some fish with a out of the norm 50% water change and wondering if high phosphates to low makes a hazard difference. I do treat the water for PH difference and make sure it matches my 7.4 aquarium as it go's in, so the only major difference in my aquarium to source water is the phosphates going from 10 PPM to 1 PPM source water and hardness going from 71 Cal/Mag to 36 Cal/Mag source, and PH from 7.4 to 7.8 source, KH is 107 to 143 source. See any water change issues here. Although I have only recently been make an attempt thoroughly test my waters, I still don’t understand their relationship with water changes with respect to this TDS thing.