I fitted an Ultra10 system to my Nelson 29 motor boat about 2 months after launching. The boat is kept in a marina berth in Poole harbour. At the time the unit was fitted growth had already begun to form on the waterline. After the unit had been in place for about 3 months I slipped the boat prior to a cruise. I was very pleased to find that the only growth was a fine slime, which was presumably that which was there before fitting. The trim tabs had algae on the top but not the underside and there was some around the stern but only at the waterline. It was quite apparent that the unit was having a very beneficial effect and had prevented further growth from forming. I am confident that the unit will keep algae at bay now that the hull has been power-washed and the unit is in operation on a clean hull.