Cleaning

• Poor water quality is a factor in encouraging certain types of algae to grow. Waste materials such as high levels of nitrates and phosphates provide nutrients for algae, so it is important to do regular partial water changes to keep these levels low. Algae that form on the glass panels of the tank should only be removed once a week or less often, if required. If you remove algae more frequently than once a week, the fish can become distressed and diseased. Never remove all the algae; leave some green algae, as they can be beneficial to the aquatic environment.
  
  

Light

• Light levels, both natural and artificial, are a major factor in algae growth. If the aquarium is by a window and exposed to a lot of direct light, or even if there is a lot of light in the room, algae are likely to grow more quickly. Direct sunlight is the worst for this and this should be resolved as soon as possible by either moving the tank or shading it with blinds or curtains. The artificial lights in an aquarium should never be on for more than 12 hours a day. Not only does this encourage algae growth, but it's bad for the fish. Eight hours of light is sufficient in a fish-only set-up.
  
  

Stock

• The stock in a tank can affect algae growth in two ways. An overstocked tank can encourage algae, as can overfeeding, due to the excess of waste produced. This organic material accumulates and creates a perfect environment for algae growth. However, you can keep certain animals in an aquarium which eat algae. These include snails, urchins and some types of crabs such as the blue-legged hermit and Sally Lightfoot crabs.
  
  

Equipment

• Certain equipment may help when trying to prevent excessive algae growth. A power filter can be useful in this way, but it will need replacing frequently. The build-up of organic material trapped by the filter will encourage the growth of algae, which is counter productive. An ultraviolet sterilizer, although generally used to rid a tank of diseases, can also be used sparingly to stop the growth of algae for a period of time. Do not use it too often or for prolonged periods, as it can be harmful to other aquarium life.