Aaaa, OK. Indeed the English isnt my native along with some 7 more languages. So I am still learning inspite I am rather fluent with, having to live many years at English speaking countries and even at homeland reading the tons of English literature every day.
You`re right, every man measures the all by own needs. Thus I know every year I need to re-paint the fouling-hit surface on my boat demanding about 3 liters of paint. If brew it myself it cost about 10 Eur, if to buy at shop factory made antifouling paint may cost between 300 and 600 Eur. Thus I am brewing myself.

And yes, those blue crystalls CuSO4. Already repaired that in my original sentence.

 

Looked for Zebra Mussels in dictionary. Indeed, the name is accurate (Dreissena polymorpha). And... strange as we are divided by 7k to 10k km... , but those nasty souls are the same sort what tries to drill holes in my boat as well.

 

RE:<<
A) Is 12 volts DC enough to ionize copper?
B) Given that the water is about 6-8 pH, what is a good distance to separate the rods?
C) Is there a way to calculate the current draw?>>
A - absolutely sure. Rather a 3 to 4 V also may happen be enough.
B - Let the distance is significantly less the face area of each electrode. Accurate value may be adjusted by measuring the Voltage at current stabilized mode.
C) First Faraday law and second Faraday law BUT everything depends on river stream velocity. And now a bad thing - the copper ions are toxic to environment. Do You really want to make a massive floating poison cloud what may lead to You environmentalists (I mean EPA) with penalty decision leaflets at the hands??

 

the copper ions are toxic to environment. Do You really want to make a massive floating poison cloud what may lead to You environmentalists (I mean EPA) with penalty decision leaflets at the hands??

Yup, that was what I pointed out to my old friend when he had the crazy idea of "in water" copper electro plating his hull. It was indeed a very crazy idea... On the other hand, copper sheathing the below water hulls of wooden sailing ships was fairly common practice back in the days of sails and oars only vessels to protect them from the ravages of the so-called "Torpedo Worm" the marine bivalve mollusk teredo navalis.

 

The bad? news is that copper sulfate at some concentrations is already in use in some lakes that folks swim in, to prevent the overgrowth of assorted marine vegetation which would make the lake useless for anything except winter ice activities. So at least in Michigan some addition of CuSO4 is permitted.
AND I would point out that what is regarded as horribly toxic in California and some other states has been found harmless in most of the USA.

 

Relative to toxicity of copper ions, I'm not certain we are talking about the same thing here.
A) Copper ionizers are an accepted technology for swimming pools to help control algae and reduce chlorine use.
B) The "Dock Disk", cited earlier in this thread, which releases copper ions into lake water, is an EPA reviewed product for repelling zebra mussels.
C) Copper Sulfate, as cited earlier, is a widely used pond algae control treatment, as well as a treatment for household sewer pipe root issues.