Algae can be very bad for fish in a pond and also make it difficult to see the swimming fish. Algae also reduce the attractiveness of the pond by giving the pond a green color. There are many methods of killing algae, but these methods should be approached carefully since some methods could harm the fish or destroy good bacteria. Bacteria fall into two categories: string bacteria that accumulates at the bottom of the small pond and plankton algae. Fortunately, with a small pond, this algae can be dealt with easily by cleaning out the pond or destroying the conditions in which algae thrives.
Remove all fish from the pond and place them in containers filled with water.
Remove all of the water from the small pond.
Sprinkle non-iodized salt on to the string algae and let it sit for 3 days.
After 3 days, clean the pond as thoroughly as possible, removing all of the string algae residue and non-iodized salt.
Refill the pond with water and put the fish back into the pond.
Block the sunlight that provides an energy source for the algae. This can be done by constructing a pond in a location that gets little sunlight or by placing plants all around the pond. These plants can block the sunlight reaching your pond and also make your pond look more attractive.
Clean your pond frequently, removing any dead organic material that falls into the pond such as leaves, fish waste and fish food. Clean the small pond up using a skimmer.
Place a net over the pond at night to further decrease the amount of debris that falls into the small pond.
Purchase beneficial pond bacteria and add it to your water. This bacteria not only keeps the fish healthy and the pond clean, but they also overwhelm algae and make it difficult for algae to grow.
Use an aerator to pump oxygen into the pond. Oxygen increases the amount of beneficial bacteria that grows in the pond and reduces the amount of harmful bacteria.