I used calcium chloride rather than calcium sulphate as it's a lot more soluble. Also used magnesium sulphate and potassium sulphate. Can't remember the exact amounts used, it was only guess work anyway. The solution made was around 2000 ppm Ca, 500 ppm Mg and 1000ppm K. I actually used potassium bicarbonate rather than sodium bicarbonate mainly to reduce the amount of sodium ions. Think I made the KH around the 10 mark. The SMS was then added to a bin and the solution was added so it nicely covered it and left for a week.

These are only figures that I guessed at but it seemed to do the trick in preventing KH from dropping when I used it in a tank.

I have also thought about adding ammonium nitrate as ammonium (NH4+) is a cation and theoretically the SMS should be able to hold it in. Even though the SMS holds all these cations in, the plant roots are able to access them.

James