Delivery fast and reliable as usual at SVB. Unfortunately, I have to write that the desired effect was missing. The stuff smells quite aggressive, but the cleaning power is not special. After an hour of exposure (shell and smallpox on the echo sounders 2 pieces), only a small part dissolved. The second donor I then treated with ordinary "Cillit Bang (lime and dirt)" and that worked much better. After about half of the time, a large part could be removed. I do not really want to advertise for household cleaners, but in this case the same is "clearly the winner" in terms of shell and smallpox removal. Whether the Yachticon now algae reliably removed I have not tested. A cleansing effect is achieved, but not as presented. But ultimately the price is inappropriate. SVB is recommended as always