Pettit Vivid, now owned by Altex. This is a hard antifoul that has been exceptional on my mates 42-foot alloy yacht for 3 years. I'm about to use the same.
Just use the cheapest antifouling you can get. Absolutely no benefit (from a corrosion perspective) in using specialised anti fouling products for aluminium. They are simply a marketing ploy by paint manufacturers. You could hang a zinc anode to give some corrosion protection.