Hair Algae is the most dreaded algae in outdoor Fish Ponds.   Hair Algae tends to grow in thick unsightly patches in nutrient-rich ponds.  It is very difficult to remove, and can be an indication of poor aeration and water quality.  The best method of controlling hair algae is prevention.  The pond should be well designed for proper water flow.  A good maintenance routine should be followed, with emphasis on mechanical filtration and proper feeding.

Once Hair Algae is present in your Koi Pond, it can be especially difficult to remove.  It will coat most anything, from the rockwork and substrate at the bottom of the pond, to the ornamental plants you are trying to grow.  The presence of Hair Algae indicates a problem.  The biggest mistake people make when dealing with hair algae is thinking they can fix it with chemicals.  Algae destroyers definitely have their place in the Koi Pond industry, but they are not a solution to the problem that caused the algae growth.   Whenever an algae destroyer is to be used, it is very important to read the label carefully.  They may contain harsh chemicals that may harm your fish, plants, or the biological filter you count on to keep your Fish Pond healthy. 

The first step to recovery from hair algae is to find out what caused the growth.  It will only grow in nutrient-rich water.  It also prefers slow moving to stagnant areas of the pond, as these will be the most nutrient rich.  Often the cause of this algae is simply overstocking and overfeeding.  Depending on your natural plant life, the biological filter can only convert so much organic waste.  The rest will remain present in the form of hair algae fertilizer, waiting for something to utilize it. 

The other common cause of Hair algae is improper aeration.  This will cause pockets of oxygen poor water in which good bacteria will not be able to grow.  This will quickly lead to conditions conducive to algae growth.  It can also lead to poor water quality, and soon stressful, disease-inducing conditions for your pond-fish.  It may be necessary to further aerate your pond, possibly by adding an additional water pump to create proper current.