Diagnose green, yellow/mustard, and black algae in a pool and apply the correct chemical treatment for each type

Steps

1. Identify the algae type by color, texture, and location: green algae typically clouds the water and coats surfaces broadly; yellow/mustard algae clings to shaded walls/steps and resists normal chlorine levels; black algae appears as dark rooted spots with a protective outer layer, usually on rough surfaces/grout
2. Brush the affected surfaces aggressively before and during treatment to break down the algae's protective layer, especially for black algae, which needs physical disruption for chemical treatment to reach it
3. Correct water balance and free chlorine to normal range first, then shock at an elevated dose appropriate to the algae severity using breakpoint-style dosing logic
4. For yellow/mustard algae, treat it as more chlorine-resistant than green algae and use a compatible algaecide in addition to shock, plus clean/replace contaminated equipment (nets, brushes, toys) that can reintroduce it
5. For black algae, brush repeatedly over several days combined with sustained high chlorine and a compatible algaecide, since its root structure can survive a single treatment
6. Run filtration continuously during treatment and clean/backwash the filter afterward to remove dead algae and prevent regrowth from filtered material