Algae is a water-born bacteria that pops up virtually out of nowhere to leave behind yellow, green, and sometimes black stains along your pool walls and floors.  Algae doesn’t need a ton of time to appear.  And if it’s not treated properly and fast, you’ll notice that little green spot turn into a swampy mess in no time.
* As a side note, the sight of algae doesn’t necessarily mean bad chemical balance or no chlorine in the pool.  Chlorine grows comfortably in pools that have enough chlorine to swim in.
Steps To Removing Algae:
1.  Brush The Entire Pool

Algae doesn’t like to be bothered.  It likes to grow in crevices and hard-to-reach areas like corners of steps, walls, and tile.  In order to rid the pool of this bacteria, the first step you need to take is removing all the algae from the walls and steps of your pool into circulation.  Depending on the severity of the algae bloom, you may have to use a metal brush as typically plastic or nylon bristles won’t be able to do the trick.
2.  Shock The Pool

Now that the algae is circulating in the pool, you must “shock” or superchlorinate the pool.  You can purchase shock from your local pool store in as small as 1 lb bags.  Depending on the severity of the algae bloom, you may need multiple lbs in order to properly kill the algae.  Simply scatter the shock in the pool, while walking around the perimeter.
3.  Run, Run, Run

Now that you’ve brushed and treated the pool, set your pool timer to allow circulation for 24 hours.  Again, depending on the severity your pool may need to circulate for longer.  Without proper circulation, all the chemicals in the world won’t get the pool clear.
4.  Clean The Filter

After allowing the pool circulate for 24+ hours, it’s very important to clean the filter out with a high pressure hose,insuring all the dead algae is gone.
Note:  If you notice after the pool clears, that algae is still present, simply follow steps 1-4 again!