Biocides and Toxins

When a bottom or propeller gets fouled, the first sign is a slime covering the bottom called biofilm, which then leads to algae growth which in turn leads to barnacles and other creatures attaching to the bottom. To combat this, anti-fouling paints contain biocides, cuprous oxide being the most popular, which are released at a controlled rate.

Hard paints contain varying levels of biocides which are released slowly on contact with water. Ablative paints generally contain lower levels of toxins but they are released at a more steady rate as fresh paint is exposed. In addition to Cuprous Oxide many paints now include a slimicide to prevent growth of slime. Slimicides include Irgarol, Biolux by Interlux, and SR Slime Resistance by Pettit.

You get what you pay for. Biocides and Slimicide, especially copper add to the cost of the paint and are expensive. Cheaper paints can be okay for colder water with fewer nutrients.