Excessive organic matter in the pond provides nutrients for algae, contributing to its growth. Algae can obscure the view of colorful fish, and more dangerously, it robs the water of valuable oxygen and releases harmful pollutants.

UV clarifiers also are effective tools that use ultraviolet light to destroy the reproductive ability of suspended algae. Dead, microscopic algae will clump together into particles large enough to be removed by filtration.

Increasing the amount of floating and oxygenating plants in your pond is another simple solution to keeping the water clean, and clear. Floating plants such as water lilies, water lettuce, lotus and water hyacinth provide shade, reducing sunlight in the pond, which helps control algae growth.

Submerged plants, also known as oxygenators, affect the carbon dioxide and oxygen levels of the pond by competing directly with algae for light and food. Oxygenators absorb nutrients from fish waste and minerals through their leaves, helping to starve algae, keeping the water clear. Some examples of oxygenators are Hornwart, Anacharis and Parrot's Feather.