I was asked about lowering GH/KH in another section and decided to move into this section since this could be informative for everyone.
Ridns asked: I used water softener pillows to soften my water but only the GH went down. It had no effect on KH, Why?
A water softener contains ion exchange resins which selectively remove calcium,magnesium, and other metals such as iron and copper. It does this by exchanging sodium ions in the resin for those minerals much like a household water softener would. This method of softening water only affects GH and has no effect on KH.
There are several ways to lower KH in your tank.
One way is to use rain water or Reverse Osmosis water and use that to replace water removed during a water change thus diluting your tank water with softer water.
Another way is to add "peat" to your filter which wil lower both kh and GH but there are several drawbacks to using peat.
1) It adds tannins to the water which ,Depending on how much you use, will turn your water yellow-brown.
2) It adds humic acids to the water which lowers ph but throws off the KH/PH/CO2 relationship and those CO2 charts become pretty much useless to determine how much CO2 is in your tank. There are CO2 test kits which do measure CO2 directly and are not affected by this function.
If you want to learn more about peat and how it works CLICK HERE