WHAT IS ALGAE?

Algae is an aquatic, plant-like organism. It is introduced to pool water as an airborne spore. There are three main types of algae:

1.    GREEN ALGAE, or chlorophyta,
     Green algae is the most common form of algae. It appears as a streaky,     slimy buildup, first noticeable on steps, in corners, and on the plastic     surfaces of skimmers and return fittings.
2.   YELLOW ALGAE, or phaeophyta
     Yellow algae, also known as brown algae or mustard algae, has the same     slimy texture as green algae, but it is more difficult to remove. Yellow algae     loves shade, and will often appear in covered pools. This form of algae     grows in a long, streaky pattern, appearing on pool walls, in corners, and on     steps and love seats.

3.    BLACK ALGAE, or cyanophyta
     Black algae is the least common form of algae, but once it blooms in a pool,     it is extremely difficult to eradicate. Black algae is usually the result of     chronically low chlorine levels: it is often found in leaky pools, where     near-daily replenishment of the pool water is necessary. As hundreds or     thousands of gallons of fill water are added to the pool, chlorine and     stabilizer levels drop, allowing black algae to gain a footing.

     Black algae first appears as small specks, often at the deepest part of the     pool, These specks rapidly develop into large, dark blue to blue-green     colored buttons, slimy to the touch and virtually impossible to brush away.     Untreated, black algae will quickly spread across the entire surface of the     swimming pool.

Another pool problem, Pink Algae, is not an algae at all, but a bacterial growth. It is slow to grow, and is easily killed by chlorination.

WHAT CAUSES ALGAE?

Algae spores are everywhere: these microscopic single-celled structures are blown into the pool by the wind, washed into the pool by rainfall, or carried into the pool on swimmers' skin or bathing suits. Under the right conditions, tiny spores will bloom into those dreaded bright green, mustard yellow, or blue-black discolorations.

Here are the key factors in algae growth:

1. Algae can develop when little or no chlorine is present. Over time, heat, sunlight, and water loss will drive down chlorine levels. The lower the chlorine level, the more likely that algae will bloom. High water temperature is a common problem in the Gulf coast climate. Weekly chlorine "shocking," coupled with application of stabilizers designed to shield residual chlorine from the effects of heat and sunlight, helps ensure that there is always sufficient chlorine in the pool. Spas, which are often heated to temperatures well above 100 degrees, are especially susceptible to algae growth.
2. Yellow algae thrives in shade. Covered pools are an inviting place for certain strains of algae. If you cover your pool, you can help minimize algae growth by periodically pulling back the cover, affording the water some sunlight and circulation.
3. Algae loves a dirty pool! Leaves and dirt offer a great growth medium for algae spores. The longer you allow leaves and other debris to sit on your pool floor, the more likely that you'll see algae. In an extremely dirty pool, algae will continue to bloom, even when residual chlorine levels rise as high as 8 to 10 parts per million!
4. Inadequate filtration will lead to algae growth.Water clarity depends on daily circulation and filtration. Anything that impedes water flow from the pool to the filter -- clogged skimmer baskets, a dirty or damaged filter, a defective pump motor, or a failure to run the pump for an adequate amount of time each day -- will encourage algae growth. The first warning sign of a filtration problem is hazy, milky water. Left unchecked, cloudy water can quickly lead to a full-fledged algae bloom.

HOW DO I PREVENT ALGAE?

1. Immediately after using the spa, turn the valves so that the pool water will flow into the spa for 20 minutes. This will replenish chlorine-dissipated spa water with chlorinated water from the main part of the pool. (Usually, just set to normal filter operation.)
2. Remove your pool cover one day per week to allow the water to "breathe".
3. Make sure baskets are free of leaves and debris.
4. Check water circulation. Clean or backwash your filter if necessary.
5. Make sure the pump timer is set to run for an adequate amount of time -- 4 to 6 hours each day in the winter, and 10 - 12 hours daily during the summer months.
6. Make sure your filter is clean and your return lines have strong water flow.
7. Some spots of dead algae may remain on your pool walls, even after chemical treatment. Brushing the pool walls with a nylon bristle pool brush will remove dead algae, and help keep live algae from forming.