I'm using Vivd anti-fouling it is very good, My boat is 50’ build from Aluminium, which is good for ultrasonic transducer
signal transmition. After some research
I found store bought Ultrasonic units of poor quality, whereby they overpromise and Under deliver.
I installed a heavy-duty ultrasonic 2 transducers custom designed by a NZ electronics
fellow, Eric Bretscher, owner of Nordkyn Design, test his invention on his sail boat. You should visit his website, there are some very good articles on his experiences and electronic solutions.
Featured Articles | Nordkyn Design
I installed two of his Ultrasonic transducers a year ago, I found the hard shell Barnacles
my Bay is known to be a problem, so far none have no hard shell or barnacle grown at all. It is not perfect solution, as I still get slim and weed around the waterline, I have a diver clean the bottom every 3 months. For him the scrubbing job is so much easier than it used to be. To sum-up my impression, in my experience so far. I will get one year for sure and possibly two extra years without having to slip and anti-foul the bottom. As all boat owners would know, the slipping and painting saving are significant as it will more than pay for its self.
PS if you install an Ultrasonic unit, I found you need an off and on switch when cleaning
the boat's bottom, and also my HF radio
gets chirping feed back when the ultrasonic unit is switched on.
Good luck with your research
in this interesting topic.