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I've not seen anyone post pH, GH, KH, TDS changes to their water mix as each ingredient is added. I've done so for interest and was surprised to discover Calcium chloride noticeably increased my pH. After researching it "CaCl2 comes from a Strong Base and a Strong Acid. For salts of strong bases and strong acids the pH will remain neutral at 7". -------------------------------------------------------------------------- 13-05-2021 Recipe. Change water is 26.5 degrees and constantly mixing via water pump. Each ingredient is cumulative. 1) 220 lt. of warmed tap water. pH 6.9, GH 1 degree or less, KH 1 degree or less, TDS 32-35. Very soft water. 2) Add 1.5g of Vitamin C Powder (wait 4-8 mins). pH 6.75. GH, KH & TDS Not tested. Resultant pH drop was expected. 3) Add 18g of Epsom Salt (Magnesium Sulphate MgSO4.7H2O). pH 6.65, GH 3, KH 1 degree or less. TDS 72-74. pH drop was expected. 4) Add 4.7g of Potassium Sulphate (K2SO4) Sulphate of Potash. pH 6.7, GH 3, KH 1 degree or less. TDS 90-93. Minimal effect on pH was expected. 5) Add 2g of Calcium chloride dihydrate (CaCl2.2H2O). pH 7.1, GH 3, KH 1 degree or less, TDS 98-101. CaCl2 noticeably increased pH! This was unexpected. 6) Add 18.5g of Calcium Sulphate (CaSO4.2H2O). pH 6.75, GH 5, KH 1 degree or less, TDS 151-156. Minimal effect on pH was expected. 7) Add 2g of Calcium Carbonate (CaCO3) Chalk. pH 6.95, GH 5, KH 1 degree, TDS 163-169. pH increase was expected. 8 ) Add 2g of Calcium Carbonate (CaCO3) Chalk. This is 4g in total. ...and 0.4g of DTPA Iron Chelate (11%). pH 7.5, GH 5.5, KH 1 degree, TDS 168-174. pH increase is expected. 9) Retested mix 1h later (water is constantly recirculated via a water pump). pH 7.5, GH 5, KH 1 degree, TDS 173-179. Curiously, GH dropped slightly even though TDS increased. 10) Retested mix 24h later (water is still, and temperature dropped to 14.4 degrees). pH 7.5, GH 6, KH 1 degree, TDS 181-187. Curiously GH has increased to 6. TDS will likely vary due to water temperature. Some parameters of final mix: Phosphate 0.00 ppm (via Hanna Checker) Mg 10-10.5 ppm (mg/l) (via JBL Test Kit) Potassium (K) ~11 ppm (via JBL Test Kit) Total Chlorine 0.00 ppm (via Hanna Checker) Free Chlorine 0.00 ppm (via Hanna Checker) - pH, GH & KH tested via API Freshwater Master Test Kit. - TDS via 2 cheap and nasty TDS Pens. Better test devices arriving in 2 weeks: - Milwaukee Instruments MW102 Pro+ pH pen. - EC59 Pro TDS and Conductivity pen. Both of these devices have calibration. -------------------------------------------------------------------------- Lessons learned: Richgro 1kg Soluble Powder Sulphate of Potash (1 Kg, $11.70 from Bunnings) works fine and tested Phosphate free, however I critically need KH. The +1 KH I get from using Potassium Bicarbonate cannot be given up. There is no interest in using Sodium Bicarbonate. -------------------------------------------------------------------------- At this stage, the recipe for next 220 lt. batch of change water is planned as follows: 1.5g of Vitamin C Powder 17g of Epsom Salt (Magnesium Sulphate MgSO4.7H2O) 5.5g of Potassium Bicarbonate (KHCO3) Buffer 20.5g of Calcium Sulphate (CaSO4.2H2O) 3.5g of Calcium Carbonate (CaCO3) Chalk 1.1g Calcium chloride dihydrate (CaCl2.2H2O) 0.4g DTPA Iron Chelate (11%) Resultant parameters from above plus my tap water will be around pH 7.0-7.4, KH 2, GH 6, TDS 160-170. Ratios Ca 4 : Mg 1 : K 1.2 -------------------------------------------------------------------------- If anyone knows of an online Australian retail store where we can buy small quantities (500g or less) of Chelated Zn-EDTA and Mn-EDTA powders, then please advise.