I run ChemPure for my carbon, ect.... I Do this kind of water change because this tank has been set up for 3 years.... but was neglected from Feb till Sep, no waterchanges or top offs..... just had a power head rotating the water..... and the level had dropped to half full through that time. I renergized it, and I have a pistol shrimp (who lived through the whole ordeal) who likes to stir up all the sediment from beneath, so I do water changes to keep up with him, and to get rid of all the sediment.... Long story long...