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Algae can certainly be an annoying problem to deal with while maintaining a water garden. Fortunately, there are many ways to keep an algae-free pond. From plants and fish to proper filtration and chemical remedies, you’ll find it’s easier than you think to keep your algae problems down to a minimum.


Under water plants such as Elodea, Hornwort, Sagittaria and Cabomba are some primary plants to consider in this equation. Ideally, one bunch for each square foot of the pond’s surface is enough. If you have a high population of fish in your pond, consider more plants to counter-balance fish waste and their grazing habits. Elodea is a great plant to help control algae because it breaks dormancy earlier than other submerged plants. Usually in bloom a month earlier than others, you’ll get a head start on controlling algae. Keep in mind that Elodea grows and spreads rapidly and will need thinning by summer.

If your pond water is already green with algae, it will take longer (usually up to six weeks) to get the problem under control. Under these circumstances, submerged plants should be moved closer to the water’s surface where they can receive more sunlight for faster growth. As the problem lessens, the plants can be moved back to their original settings. Ponds that have up to four inches of pea gravel at the bottom are ideal for the “tame” Dwarf Sagittaria that roots directly into the gravel. Ponds with Dwarf Sagittaria are unlikely to experience any green water algae problems at all.

Sunlight not only helps submerged plants grow but also greatly aids in feeding algae so covering your pond with floating plants is ideal. A general rule of thumb is to cover one-third to two-thirds of the water’s surface with plants such as lily pads and floating plants such as Water Hyacinth, Water Lettuce, Fairy Moss and Duckweed to name a few.

Surface shading isn’t necessary in keeping a pond clear of green water algae, however it is much more difficult to maintain a pond without it and will require many more submerged plants. As stated earlier, Dwarf Sagittaria carpeted along the bottom will help compete with algae for the available nutrients.

Water and other natural remedies

Changing out the water to rid of green water will prove only to be a temporary solution because you’ll just be feeding the algae nutrient-rich water and the frequent changes will actually stress out your fish and plants.

Be sure to follow directions carefully when using plant fertilizers because too much can aid to the growth of algae and also be a risk to fish. On the same topic of plants, use heavy garden soil rather than humus-enriched soils because they are unnecessary for aquatics and only feed algae more.

As contradictory as it sounds, fish waste adds nutrients to the water as well so keep fish population within the recommendations of your pond size. Only feed your fish what they’ll eat in five minutes and scoop out what’s left over with a net as uneaten food will also contribute to algae’s dinner. A skimmer can also come in handy to filter out floating food, debris, leaves etc…

Nitrifying bacteria (often found in bio-filters) can be added directly to water. This bacterium requires circulating water, proper pH levels and the right temperatures. If set in the proper conditions, it can aid to temporary clearing of green water algae. The right amount of submerged plants is important because the plants will utilize the bacteria’s nitrate end-product to help keep the algae from coming back.

Water fleas, tadpoles and snails are a great team with janitorial qualities. Water fleas will eat the floating algae. Tadpoles will eat the filamentous forms of algae. While toad tadpoles will spend a short amount of time in the pond, frog tadpoles can spend up to two years in a pond before morphing into frogs. Snails (Ramshorn, Trapdoor and Apple) will feed upon the tufted algae that grow on pots or liner. Some snails have been known to eat the plants so keeping an eye out for such damage is recommended. One snail per square foot of water surface is the recommended stocking rate for snails and the Great Pond Snail should be avoided and or removed as it multiplies rapidly and feeds on aquatic plants.

Salt in the proper doses will kill algae.

After bashing algae and educating you on many ways of killing it in the past 800 words, keep in mind that in moderation, the smooth algae on the sides of the pond and coating on your submerged pots is a sign of a healthy pond.

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