I am a bit skeptical on the Vid.
I dont think your going to wipe some gel stains off like that with a solution of oxalic acid.
OA would do great for Rust .. but not for organic growth/grime on a plastic hull ( its not rust ).
I have seen some other acids that work like what the Vid shows .. but its not OA.
You think other Main production hull cleaners Dont use such a simple product and sell them for Millions because its too simple ?
OA in a squirt bottle that sells for 9.95/qt solves your bottom boat stains? .. Its not going to work like this.
LOL.
I think this is Fake. I could be wrong ..
Soft scrub with bleach and some water will kill All growth and algae/stains. A few passes with a scrub brush and a hose will leave your hull nice and clean
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YD.