Anti-foul in fresh water?

I’m still confused about the necessity for regular hull cleanings and air-foul reapplications in FRESH WATER. All I can see is a thin layer of algae. In theory that might have some minuscule effect on performance through the water, but in a big tub of a trawler like mine, I doubt that’s significant. So what else? Can algae impact the integrity of the fiberglass hull? At what point does it become too much, too long?

Ive never really seen it grow long. Even in warmer harbors. It is usually pretty easy to power wash it off. I've never seen anyone pull a fresh water boat mid season for a bottom wash.

Probably don't need the antifouling additives but everyone uses it.

pete

Fresh water definitely doesn't require nearly as heavy duty of antifouling as warm salt water. It's still helpful to have something to reduce the growth and/or make it easier to remove though.

You can go years in fresh water. But you still need to remember your zincs.

I am in fresh water almost exclusively. I get slime and some really weird pod-like creatures start growing on anything not coated in anti-fouling. We have to pull out each year due to ice so the marina cleans the bottom every year weather we want it or not. You don't want to let slime dry. It becomes like concrete. New anodes every year although I don't think they are Zinc. Probably Aluminum or Magnesium.

Up here zebra mussel can grow in incredibly big chunks on the hull. I have seen a boat with something like 10kg of mussels hanging from the hull. Not sure I would like my bottom to looks like a dock pile.

L

Here in FL the water in Lake O does not seem to promote any type of growth.


Folks that come to hide in the Hurricane Hole area seem to leave with cleaner bottoms than they arrived with.

Our boat is also exclusively in freshwater now, Missouri River. We bought the boat in Newport, RI though and it had just had a very nice anti-fouling bottom job done in 2015. Our section of the Missouri is also heavily contaminated with zebra mussels but they don't seem to attach to hulls very much, coated or otherwise, or the aluminum pontoons for that matter, at least not around here. They do cover intake grates and screens really badly though, and the dock structures and if you leave a line trailing in the water for even a week the mussel buildup is astounding. They do build up badly on the bottom of our rubber (pvc) dingy, takes dynamite and laser beams to blast them off. I have been thinking of doing an anti-fouling coating on the dingy, as I recall they make a/f paint for pvc and hypalon. As for the boats in our marina though, anti-fouled or naked, we usually just get a thin slippery layer of river slime on the hull that comes off with a pressure washer pretty easily at the end of each season. (The post above that talks about zebra mussel build-up on hulls is interesting to me, doesn't seem to happen as much here, although they do build up like crazy on other surfaces. Maybe the slime layer on the hulls here makes them more inclined to attached to other surfaces instead.)

We are exclusively fresh water and although I have seen boats with hair growing 3 inches long it is primarily because the boats don't move all summer. Anyone that uses their boats usually gets, as others have said, just a slime layer. So why use antifouling, well the slime comes off with a pressure washer easily in the fall if you do it right away on haulout. On many boats with no antifouling that have been left in the water all summer, it is necessary to use some acid and some scrubbing to get the hull clean again.