Algae growths can start in well lit, warm, and shallow pool waters. In order to keep a pool clean, the water must be well sanitized. Algae feed off of sunlight and minerals found in pools and spas that are not sanitized. The by products of many types of algae can breed dangerous bacteria and germs. If those germs and bacteria are left to grow unchallenged, they will eventually make your pool water unsafe and unsanitary for human use.
The formation of algae in a pool or spa can be prevented with proper sanitation. If pool water is not routinely sanitized, algae will begin to form in the shallower regions of your waters that receive good amounts of sunlight on a day-to-day basis. Algae are tenacious, and can still sometimes thrive in well sanitized waters.
The three most common types of pool algae are yellow algae, black algae, and green algae.
The most difficult type of algae many homeowners are forced to deal with is black algae. Black algae is a dark blue-green in color, but is known by its earlier stages of tiny black specks on the pool floor. These specks grow rather slowly at first, but as soon as they become noticeably larger, they will quickly cover the bottom of your pool.
Not only will black algae expand to make your pool look filthy, it can also cause permanent structural damage. Black algae grow deep into your pool plaster and concrete walls. If it is allowed to grow unchecked, the algae expand the cracks making them nearly impossible to fix. Black algae are highly resistant, and can survive with little light in deeper regions of the pool. Black algae, like other algae, can be prevented with the application of algaecides, and regular sanitation.
You might have seen the second type of algae in a pool that has been out of use for some time. Green algae appear to the naked eye as a layer of green slime floating on the surface of a pool. The slime can be easily removed using a pool brush or net, but it remains invisible in the water. Green algae grow rapidly and the only way to remove it completely from your pool or spa is to combat the aquatic plant with chemicals. Green algae is the most common form of pool algae and almost every pool owner has experience it at one time or another.
The third type of algae is yellow algae. Yellow algae grow slower than green algae, but are harder to eradicate. The visible colonies of yellow algae can be scraped off pool walls, exposing its base layer to the chlorine and algaecides that are hopefully abundant in your pool or spa. The best way to remove yellow algae is through a process known as super chlorination.
Brushing off algae growths is usually an effective method of removal with fiberglass pools or other smooth walled pools. Plaster, another common pool construction material, is a little trickier. All of the cracks, pores, and crevices in a plaster walled pool are great for harboring growths of unwanted algae. Algae will expand and feed off of the plaster, sometimes causing irreversible damage. The most damaging form of algae for a plaster pool is black algae. Not only is it stubborn and difficult to remove, it will form a protective, hard shell around itself. The hard shell makes it removal of the algae very difficult.
If brushing and chlorine are not enough to keep your pool clean, super chlorination is the next logical step. Super chlorination is the process of shocking your pool or spa waters with massive amounts of sanitizer. This shocks anything living in the pool, and after the chemicals dilute, the pool is ready to go. If this fails, consider hiring a professional pool cleaner.