If you're in an area that restricts the use of copper-based bottom paints, you can use a bottom paint that contains the potent, copper-free biocide ECONEA® and/or zinc. Examples include TotalBoat Krypton, TotalBoat AlumiPaint AF, Pettit Ultima ECO, Pettit ECO HRT, Interlux Micron CF, Interlux Pacifica Plus, and Sea Hawk Smart Solution.
Another option worth noting is to use a super-slick, biocide-free coating, such as PropSpeed, that works by shedding marine growth before it can attach to your hull and any underwater metal parts.