Since most of the paints in our tests have had no problem warding off hard growth, the ratings were ultimately based on a paint’s ability to deter the growth of slime and soft growth. Twenty-two of the 52 paints tested include an anti-slime additive. But none of the paints that received the highest overall scores (combinations of Excellent and Good ratings in both locales) contain anti-slime ingredients.

The additives are actually pesticides. The two most common are Irgarol, an algaecide made by Ciba Specialty Chemicals for marine None of the top-performing paints in our test include an anti-slime additive.use, and Zinc Omadine, a trade name for Zinc Pyrithione. Each manufacturer…