Forgot to mention the tank is 260 litres.

I am aware of biogenic decalcification taking place in the water, my tank doesn't seem to suffer this process to often. The pH is generally quite stable. The problem is the water in my R/O vat, just can't seem to get the pH at 6.8-7.0 with a KH of 3 or 4. I have even tried the phosphate free method as recommended by KENT, still couldn't do it. I e mailed them with this problem, they just said not to worry about as it is fine for a pH reading such as this to have such a low KH!


Thanx