Expert: Lynn bellay - 9/12/2009

Question
hi i am a new pool manager and was thrown in at the deep end so to speak and since i have been here we had a new dosing system fitted which since then the pool has formed black algae i have lowered the pH and raised the chlorine and my alk levels are at 140 and calcium is very very low on 100 how can i resolve the black algae please please help me many thanks ben

Answer
Blue green [black algae] is very difficult to cure.I take it its plaster commercial pool.You don't say how heavy it is so I will start with the simplest cure.Keep the ph at 7.0I do not know the capacity of your pool,but I would use 10 gallons of liquid chlorine around perimeter of pool.Run the filter for 24 hours and brush with a ss brush.Of  course do not swim until chlorine is normal.If this does not work or algae is heavy you will need to shut down for about 2 weeks.You will need 10 gallon of chlorine,2 gallons of amonia hydroxide and muriatic acid.Add the chlorine and run filter for 24 hours,add ammonia hydroxide be careful of dangerous gases that will develop,add muriatic acid in the areas of heavy growth.THIS IS VERY DANGEROUS USE EXTREME CARE GLOVES, MASK, ISOLATE POOL FOR 2 WEEKS continue to brush.I hope the less evasive cure works.LYNN