How do I kill black algae without resorting to heavy metals?
vinyl or concrete(marcite, gunite)? You're using salt, right?
If it's vinyl, goto your local
Pinch A Penny //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif and buy 1qt of Super Metal Control, 1qt Super Black Agleacide. Pour the metal control in and let it circulate for atleast 8hrs. Brush it frequently doing this duration. Turn your chlorinator up to shocking level(super chlorinate) and 24hrs later pour in the black algeacide and scrub, scrub, scrub!
Black alge has very hard heads. lol So they're stubborn to most chlorine levels. The metal control will help loosen them so the chlorine can penitrate them and the black algeacide can finish them off.
If it's concrete, turn off your pump, and get a bunch of chlorine tablets together and beat the shit out of them until it's a fine powder. Then pour over the infected area and let it sit for 24hrs. Then scrub with a steel brush.
Only do this method if your marcite has never been painted!
Black algea is brought on by low sanitizer levels, ala chlorine. Add more salt. Add 40lbs per 5k gallons. Or lots of liquid bleach.