This past weekend I put up an 18' x 4' swimming pool and filled it. By the time it was full last night it was too late to get out and install the filter (3AM) so I put it off until this morning. I go out about 9:30 this morning and the water is pea green. Yuck! I didn't expect to get an algae bloom overnight within 6 hours. After initial set-up was complete, I checked my water and the pH was 6.8. The set up instructions for the pool said to add pH increaser until desired level was achieved before chlorinating. So I added the increaser and waited a couple hours and rechecked. The pH was 7.2. The instructions then said to shock the pool so I did that and it jumped the pH up to over 8. What's the best way to rid the pool of algae? I changed the filter cartridge after about 6 hours of operation because it had turned solid black and the water in the filter housing was black too.