A friend that boats around the world said many yacht owners are buying copper powder to put in their bottom paint. He said you can go to a local craft store and purchase or order online and its very cheap and you don't have barnacle issues anymore.
You could. Also putting a 8 ounce bottle of cayenne pepper works good as well. Copper could cause color change in black and you,d see green on the waterline where it’s oxidizing
Most copper bottom paint contains 20%-70% copper. I can't see where adding would help if you already use a high concentrate paint. Another point, although you're in Florida, it probably won't be long before someone on the the east coast starts a pogrom to eleminate copper like they have on the left coast. As of Jan. 2020, in Washington copper paint in concentrations of over 0.5% will be completely banned for recreational boats 65 ft. and under, with fines as much as $10,000 a day! California, of course, is soon to follow. There's an excellent article in the Feb. 2012 BoatUS magazine about it. It's dated but still relevant, I think. You can Google it. Worth a read.
I am located in WA and have no plans to stop using Seahawk Cukote which is 47% copper content. I do my own bottom work and will be watching this closely on enforcement. Cukote works very well in our waters.
Aren't there some federal and local limits on copper content? Best thing for reducing barnacles is run it?
Fishermen added arsenic and copper to bottom paint and went 3+ years in salt water on the West Coast. http://coppercoatusa.com/ claims 10+ years.