Flocking a pool is a process of using a chemical called flocculant or pool floc to clump together tiny particles in the pool that cause cloudy water. The flocculant attracts floating particles in the water that are too small and light to sink to the bottom to be vacuumed up, such as bacteria, viruses, algae spores, and other microscopic debris. When you pour the floc in the pool, it makes all these particles clump together in big chunks so that they are heavy enough to sink to the bottom of the pool, where they can be vacuumed up or sucked toward the filter. Flocculants are a great way to clear up a pool fast, but they require more work than pool clarifiers. Once the clumps form on the bottom of the pool, youll need to remove them with a manual pool vacuum, as an automatic pool vacuum will not work. Its important to note that flocking is an extreme treatment and should only be used when other methods of clearing up the pool arent working.