There are a few reasons your pool is cloudy. Could be poor filtration/circulation or even unbalanced water. Pool needs proper daily circulation as well as proper chlorination. Pools typically appear cloudy after heavy rain storms or pool parties. If you ever see visible algae growth, best practice is to shock pool according to package instructions followed up with weekly treatments of algicide. If your pool isn’t looking as clear as it normally does and you have already shocked and balanced your water, its time to CLEAN THE FILTER.