On Pettit's brand of paints with high copper content, they use "Cuprous Oxide". Read the label for the ingredients and formulation.
That means "Oxidized Copper", yes, the greenish patina that Copper gets after it has been in contact with an oxidizing agent like oxygen or sea water
Being an Engineer
for heavy industries and learning
about Metallurgy, even if the Copper used for this mixing with paint
is not as pure as Bullion, the oxidation still occurs, bleeds off the poisons and keeps killing the hard organisms that want to attach to the surface. Does not do much for algae or slime or weeds so you can still come and scrub once a month, but makes the scrubbing work easier and that 'evidence' you mentioned you needed, is in my bottom paint
concoction, which has lasted over 5 years.
Copper is 'still legal' to use until it 'environ-mentalists', accent on 'mentalists' ban it and makes us rip out and away all the plumbing
from well built houses. Copper can be bought on Ebay for about $10 for the amount of Copper in powder form I would be using again next time, so it is not 'expensive' as you say.
Try it before shooting it down, it will not affect the waters, the fish
, your health
or your own livelyhood. Respectfully, ..Really.