After less than good results, in fact practically no results on the caked growth. I am looking for more suggestions. Used Zing Aluminum Pontoon Cleaner, about $35 for a gallon, recommended highly by a boat supply store. Didn't do squat for the caked on growth. Made the aluminum above the waterline look great. I have a question about the different suggestions that have been made, Alumibrite, muriatic acid, what have you. Have you used the product on pontoons that probably haven't been cleaned for years? The stuff is 1/16" to 1/8" thick in some areas. My next product, I would like to be something that actually will remove the stuff. Could I get some feedback from some of you who have had really bad growth and were able to remove it without resorting to a sander or grinder? Right now, I am totally lost. (That happens a lot though, so I don't get too worked up about things.)<br /><br />Charles