How can I get green algae off the bottom of a boat?
Pat from Canyon Lake, California
---> BLEACH (not on wooden boats, OK for fiberglass or plastic) Please test this in a spot first!
---> Use rubber gloves & a sponge with a Scrubby side. (The larger green sponges avail. at most grocery stores)
Have a fan running in a garage or better yet do this outside. Wipe straight bleach (or half water/half bleach) on boat bottom with the sponge side, wait about a minute, then scrub with the scrubby side of the sponge & rinse well with your hose.
Use oxalic acid to remove the algae from your boat hull. Oxalic acid, which is a white powder, can be purchased in the pharmacy section of drugstores and discount department stores like Walmart. You won't find it over the counter because it is poisonous, and you will probably have to ask for it directly at the pharmacy. If they don't have it in stock, they can order it for you. Also, I would make sure you tell them what you are using it for if you get any funny looks. In addition, you may be asked to sign for it when you buy it. Now for how to use this to clean your hull: The easiest way to clean a decent sized boat is to use a garden sprayer. If you have a small boat like a rowboat, you could use a regular spray bottle if you don't have a garden sprayer. Fill the sprayer with about a gallon of hot water and add about a half of a pound of the oxalic acid to the hot water and stir before pressurizing the sprayer. After that, spray your surface and let it sit for 10 to 15 minutes, then rinse thoroughly with fresh water. You will actually see it start to work pretty quickly. Don't be afraid of this product because it is poisonous. It is much less caustic than some of the other chemicals I have heard of people using for this job, and it also works better than some of the products made for this purpose, like Slimy Grimy, etc. Just take any precautions mentioned on the label and wear eye protection. Oxalic acid is an oxidizing agent,and it may bleach wood, so I'm not sure if you would want to use it on wood unless you tried a test spot first. Also, for whatever reason, maybe a chemical reaction, it will NOT work on aluminum at all. However, it works great on fiberglass boat hulls. You didn't say what your boat is made of, so I hope it is fiberglass. Hope this info is helpful!
Tori in PA