Algae Going Back Into Pool

I have an above ground pool with a cartridge filter. I have shocked and treated the pool with algaecide.

The water just looks cloudy. But when I vacuum the algae is shooting back into the pool through the return. I have cleaned the cartridge and it does not seem to help. Any ideas?



Hi. What is coming through the filter is algae. Algae is made of small enough particles to blow right through sand and cartridge filters. It takes a combination of shock treatment, algaecide, and running the filter 24/7. Running the filter nonstop is the part most people do not do. Any time you have water problems let the filter run until the problem is gone.

Water problems are normally caused by not shocking the pool every two weeks during the hot months and not running the filter enough. The hotter it gets the more the filter needs to run. Some smaller units will only keep a pool clean if run twenty hours or more a day.