I'm considering three kinds of chemical treatment, but I am not sure of effectiveness or risks to plants or to the pond we have about 2 yards distant (it does have a constant good flow of water to cleanse it. Chemical treatments under consideration: dichlorophen, iron sulphate, and copper sulphate.

Any advice or experience appreciated.

We have very mild but wet winters and moss takes over all my rockery, growing rapidly all over the stone walls and the soil and submerging the rock plants. Many of these die off because their stems and roots are submerged in moss which is a constantly wet sponge. I've tried improving drainage, adding lime, placing gravel around the plants etc., to no avail. It is impossible to comb the moss out of many of the creeeping rockery plants. It's not really a drainage problem: the moss proliferates all over the stone walls. Its basically a mild wet winter climate. Oddly, we don't get a moss problem in the lawn, probably because we allow the grass to grow in winter to say 3inches (or maybe its just too wet to cut!)