A flocculant is a chemical agent designed to restore clarity to cloudy water. The fundamental answer to whether flocculant kills algae is no; its function is purely physical, acting as a powerful water clarifier. A flocculant works by gathering tiny suspended particles, including dead algae cells, into large, heavy masses. This process aids in the physical removal of the matter from the water, but it does not contain the necessary compounds to destroy living organisms.
How Flocculants Work
Flocculation is a process of particle aggregation within a liquid. Suspended particles in water, such as dirt and algae, typically carry a slight negative electrical charge. This charge causes the particles to repel each other, keeping them dispersed and resulting in a cloudy appearance.
The flocculant chemical introduces positively charged ions into the water, which neutralize the negative surface charges on the suspended particles. Once the repulsive charges are eliminated, particles collide and bind together. These newly formed, larger clusters are called “flocs,” and they quickly grow heavy enough to overcome the water’s current and sink to the bottom. This mechanism is distinct from a pool clarifier, which causes particles to clump into smaller masses that are captured by the existing filtration system, whereas flocculants force the matter to settle for manual removal.
Flocculant vs. Algaecide
Flocculant and algaecide serve two sequential purposes in addressing an algae bloom. Algaecides are chemical treatments specifically formulated to destroy living algae organisms by breaking down their cellular structure. This action effectively kills the algae, turning the water from green to a cloudy gray or white color as the dead cells become suspended.
A flocculant is a clean-up tool used after the killing agent has done its work. If a flocculant were applied to a pool full of living algae, it might temporarily clump some of the organisms, but it would not prevent the surviving algae from reproducing. Successful treatment requires applying algaecide first to kill the organisms, followed by flocculant to consolidate the remaining dead matter. Using the flocculant first would leave behind live algae spores, allowing the bloom to quickly return.
The Process of Algae Removal Using Flocculant
Before applying any chemical, it is important to test and balance the water’s pH level, ideally adjusting it to a range of 7.2 to 7.6. This balanced chemistry ensures that the algaecide and the flocculant can both work at their maximum efficiency. The first step is to apply a powerful algaecide or a high dose of chlorine (shocking) to kill all living algae.
Once the algae have died and the water has changed color, the flocculant is added according to the manufacturer’s directions, often after being diluted in water. The pool’s pump should be run for one to two hours to ensure the flocculant is evenly dispersed throughout the water volume. After this brief circulation period, the pump must be shut off completely to prevent any water movement that would disrupt the settling process. The water should be left undisturbed for a minimum of 8 to 12 hours, though a full overnight period of 24 hours is often recommended for heavy algae blooms.
During this resting period, the flocculant attracts the dead algae particles, forming the heavy flocs that sink to the floor of the pool. The final step is to physically remove this settled layer of debris. This is accomplished by vacuuming the material directly to waste, bypassing the pool’s filter entirely. Setting the filter valve to the “Waste” or “Drain” position prevents the massive amount of debris from instantly clogging the filter media, which would force the dirt back into the pool.