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How to Keep a Goldfish Pond from Turning Green

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Watching colorful goldfish swim languidly around a backyard pond is one of life's little delights. Whether you have a large natural pond, a small 40-gallon plastic pond or anything in between, you have to be vigilant so you can continue to enjoy your fish. Crystal-clear water not only improves your view, but helps keep your fish healthy. You have several weapons in the battle against algae that can take over your pond and turn it an ugly, murky green.

Step 1

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Provide shade for your pond by planting leafy foliage around it and ensure only filtered sunlight can reach the pond. If you have a small man-made pond created from a pond-liner purchased at a home improvement store, try planting a container garden around the pond so you can move the plants around to see where they will best provide shade. If yours is a large natural pond, plant large trees and shrubbery around the perimeter of the pond. Algae needs sunlight to survive so if you cut off the direct sunlight, you are taking a big step toward eliminating the algae. If the pond is small enough, use beach umbrellas during hot weather to provide shade that will help cool the water as well as killing algae.

Step 2

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Measure your pond so you know exactly how many gallons of water it contains. This will help you make educated choices for filtration and chemicals. Multiply the cubic footage of your pond by 7.5 to arrive at the volume in gallons.

Step 3

Install a high-quality pond filter made specifically for the size of your pond. A filter is critical, whether you are caring for a large pond or a 40-gallon plastic pond. Algae is nourished by organic waste produced by fish and decaying leaves, so if you keep a filter running all the time and maintain it properly you will be cutting off another resource needed for algae to survive.

Step 4

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Install aquatic plants to help curb algae. Their presence inhibits algae growth by using up the oxygen in the water needed by the algae to grow. Some plants that work well for this purpose are those that grow entirely submerged, such as giant baby tears and beanstalks. Plants that root in the substrate but have large, circular leaves that float on the surface are also effective and have the added advantage of providing shade for the fish. Water poppies and water lilies are two such examples. Some plants float entirely on the water, and some are rooted in the substrate but grow tall above the surface of the water. Water hyacinths and watercress are two gorgeous, colorful flowering plants that are very effective in removing algae.

Step 5

Toss some some bales of clean, organic barley straw into the pond, if it is larger, and allow the algae to attach itself to the barley, then rake out the barley.

Step 6

Add some algae-eaters to your fish collection. These fish get along well with other fish and are low-maintenance. Examples of algae-eating fish include black mollies, several varieties of catfish, plecos and barbs.