On Sun, 28 Oct 2007 06:16:05 -0400, "Reginald P. Smithers III"
wrote:

I have always use a
product called "On and Off Hull and Bottom Cleaner". I think it has
muriatic acid, but really am not sure. I have purchased it at West
Marine and my marina's store, so I think it is readily available at all
Marine Supply Stores.

"On and Off" works extremely well. It should, the main ingredient is
hydrochloric acid. It does not seem to harm fiberglass but it will
damage some kinds of paint and take wax off the hull. I wear rubber
gloves and glasses when I use it, wet everything down in advance, and
rinse well afterward. The best way to avoid slime build up is a good
coat of wax. Zud and Soft Scrub are two of the worst things you can
use on a fiberglass boat, try everything else first.