Just Black algae or yellow as well?

[drsusan]

I have black algae spots around the sides of our inground plaster pool badly this year too. Water looks great, but black algae spots are ugly! We have been rubbing them off with wire brush but now yellow green residual stains show. Maybe we have mustard algae too? I doubt I could use a pressure hose to remove the spots but would try it if I could!

 

[ajw22]

You have to do more then brush black algae to fully get rid of it.

@Katodude who has experience with it says:

For Black Algae you are going to have to disrupt the surface of the algae physically. You can use a wire brush, which I dont like. If it is just a few spots put on a mask and snorkel and go into the pool and pick at it with a bamboo BBQ skewer.

If you have more than just a few spots, get in the pool with a weak pressure washer and you can use that to blast away the BA.

After you have physically disrupted the BA. You should dose it with LC. Get the strongest LC you can find and if the BA is close to the edges pour the chlorine down the side where it washes over where the BA used to be. If the BA is all over the place you can fill a 1 gallon pump sprayer and get into the pool and spray those spots. And yes you can do this all under water.

Then you need to keep your FC at 20% of CYA for the next several weeks.