That picture is from March, when the boat was brand new. I have Sharkhide as well and I would scrub them with a brush every 2-3 weeks but I still have a nice build of sludge and my top speed has tanked. I don’t think it was doing much. Time to switch to something more aggressive. I still have another month+ of boating season left.
I don't have Sharkhide and my boat stays in the water from March to Nov. I acid wash every November and then use the green Scothbrite pads while the boat is in the water. I get the ones that are about 6" x 9" from Home Depot.
I've got Sharkhide applied and we float around and wipe the toons everytime we go out. I use a large sponge or dish towel. The crap still sticks to the toons but the Sharkhide makes it easier to just wipe off.....
Took about 1.5 hrs but I successfully scrubbed all the grime off the toons. Got all my speed and rpm back. Couldn’t be happier. Now I need to get into a habit of doing it 1x/month so it won’t get so bad.
I have short-handle and long-handle stiff-bristle polypropylene brushes that I use 2-3 times a year when beached up at some island. They are very inexpensive at most any discount joint. Knocking off even light growth adds 2-3 MPH for our modestly powered pontoon.