Just thought of a possible flaw in my test. The control sample was taken from a water line right at the pond pump while the K/sul sample was taken from water that ran through the drip irrigation and plumbing. Is it possible for chloride to build up in the plumbing? Thus water going through it would pick up extra chloride ions while the line at my pump doesn’t go through all that plumbing to pick up extra chloride ions. I doubt that would be it but just wondering.