Need Help on Algae in my Swimming Pool!!

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When I got up this morning I discovered that my back yard swimming pool had turned green. That is the beginning of algea growth. Fortunately it hasnt got to the stage where aglea growth has adheared to the sides and walls, its simply floating around the water. I know its my fault. I had noticed that the alkalinity was very low a few days ago. I had kept the chlorine level up, although that fell over the past 2 days, & the PH is low too. I just raced outside then & put a heap of chlorine in. I know that is not enough. Would just buying alkalinity increaser be enough to kill off the algea? Or would I need to buy algaecide as well? Or a PH increaser? Or all three? I do need to keep my costs as low as possible, but on the other hand, if I dont treat it early, it will be more expensive to clear up. Hope there are My Lotters out there who know about pool maintenance. Thanks.