anything with an acid base will work , the more acid you have the easier it will work
Muratic acid is nasty to work with , if your going to use anything that strong be extra cautious and rinse everything with soap
regular toilet bowl cleaner or lime away much easier to work with
I used to sell a wax at the local marina that worked great to deter this and spotting
pricey wax and only applied by hand , but was truly a full season wax
found it
http://www.collinite.com/marine-wax/