returns shooting out white water after adding algaecide??

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My pool had alot of algae so I added a gallon of algaecide (the brand was cal -- something) -- the directions said to add the whole gallon around the pool and a little in each skimmer---- as soon as I added to the skimmer, the returns starting shooting out white powdery water instead of the clear water that was coming out b4 I added the algaecide --- the top of the pool got all white and slimey green algae was swirling around with it. I backwashed, added earth and when I started the filter again, the returns run normal for a few minutes but then go into that heavy white water again??? Please help!!