Algae Blooms

• Algae are microscopic plants that thrive in still water. An algae bloom can quickly transform your pool into a murky mess. The most common types of algae found in pools are green, mustard and black algae. Because of its color, green algae is readily identifiable and it is unlikely that a pool owner would mistake a green algae bloom for dirt. Mustard algae, on the other hand, with its yellow-brown color and its habit of clinging to pool surfaces, is often mistaken for dirt. To determine whether you are dealing with dirt or a mustard algae bloom, feel the surface -- a slippery feel indicates an algae bloom and a rough, gritty feel denotes dirt. Black algae presents as dark-colored spots on the sides or bottom of the pool.
  
  

Dead Algae

• Dead algae sinks to the bottom of the pool, often taking on the appearance of sand or dirt. Even green algae turns a brownish color when dead. The dead particles will cloud the water if disturbed by bathers or by activation of the filter pump -- but because the particles are so fine, they are likely to pass through the filter, returning to the pool to settle again when the water is still.
  
  

Solutions

• If you have identified a live algae bloom, remove it from pool surfaces by scrubbing before treating the water with chemicals. This is necessary because the algae bloom forms a natural film, making it resistant to chemical treatment. Add chlorine according to the size and nature of your pool, in line with the manufacturer's instructions, and circulate through the filter. Use a pool vacuum to remove dead algae from the bottom of the pool, together with any dirt that has passed through the filter. Test and readjust the chemical balance of the water.
  
  

Considerations

• Maintaining the correct water balance and regularly skimming and vacuuming dirt and debris from your pool will help to prevent algae growth. Adding an algicide will also help to prevent algae. If in any doubt about the nature of the matter in your pool -- live algae, dead algae or dirt -- treat on the assumption that you are dealing with a live bloom because, once established, algae can become a constant headache for a pool owner.