Applied Biochemists Black Algaetrine - 1 Gallon - 406304 by Applied Biochemists

Had black algae spots last season and again this season trying several different products and constant scrubbing. Couldn't get rid of. Was Advised by our New Pool Company, Shock 5 times normallydo, Pour in gallonof Biochemists Black ALgaetrine for our 21,000 gallon pool. Put pool brushes in pool to clean, Clean pool floats, Scrub every day, vacuum, After week/week 1/2, it was gone and I havemaintained it for the past two months with doing the maintenance weekly with 2 lbs shock and 12 oz of Black Algaetrine. Amazing product!