Clean a Pond

Ponds make for beautiful and relaxing natural displays. Yours may have a lovely water fountain or a bunch of koi. However, algae can quickly overwhelm your pond. A single-celled type of algae turns the water green and string algae covers the top of the water. In addition, decaying plant matter leaves a sludge at the bottom of the pond. To clean a pond, fish out string algae, treat the water with hydrogen peroxide or barley straw, maintain the pond with aeration, and remove plant debris with a pond vacuum or by pumping out the water.

Steps

Clearing out Algae

  1. Remove string algae with a brush, net, or your hand. String algae, which looks like strands of hair floating on the water or clinging to the walls, harms the pond’s ecosystem. A scrub brush such as a toilet brush can be used to lift up and remove the algae. Skimming nets from a home improvement store also help reach the algae, but you can also yank out the algae by hand.[1]
    • Some string algae is beneficial to the pond’s health. The algae that sticks on the pool liner, as long as its growth is under control, protects fish and combats green water caused by other algae. Try to control the algae using natural maintenance methods such as by adding plants, aerating the water, and removing waste yearly.[2]
  2. Add hydrogen peroxide for quick water treatment. When your pond is very green, hydrogen peroxide may clear up the algae faster. Add about one pint (.48 L) of store-bought hydrogen peroxide for every 1,000 gallons (3785.4 L) of pond water. Dilute it if possible by letting it run with a fountain, waterfall, or other moving water.[3]
    • Results will vary between ponds, but you can increase the amount of hydrogen peroxide as needed. Be careful though, because it can harm fish and plants.
    • Chemicals such as String Algae Control are less harmful but more expensive options for existing algae problems.
  3. Add barley straw for a natural treatment. Purchase barley straw online or at a garden center. Stuff the straw into a mesh bag, hay net, or fishnet tights. Allow the bag to sit in the pond for several weeks, preferably where the water spreads, such as a fountain or waterfall, if possible. After a few weeks, the barley will start to degrade. Remove any rotting pieces to avoid adding more nutrients for the algae.[4]

Maintaining the Pond

  1. Install a UV clarifier. UV lights treat the single-celled algae that causes green water. The UV light is installed in the water. Water passes through the light and the algae gets destroyed. The light needs to be replaced yearly and brought in during winter months.[5]
  2. Rinse your pond filter. Your pond may have a filter, which is useful for growing bacteria that breaks down waste and food when you have lots of fish. If it is difficult for water to flow through the filter, follow the owner’s manual to clean the filter. Only use pond water so that you preserve the helpful bacteria in the filter.[6]
  3. Introduce plants. Plants are a way to naturally keep the pond clean and clear of algae. Plants such as anacharis, hornwort, and parrot’s feather live under the water and keep the water full of oxygen, which limits algae growth. Lilies and lotus plants also cover the surface of the water, blocking sunlight that aids excessive algae growth.[7]
    • You introduce plants by planting them at appropriate layers. For example, submerged plants such as anarachis rests fully below the surface with its roots in a basket. Marginal plants, including cattails, and lilies are rooted in water with aquatic potting soil. Floating plants such as water hyacinths rest on the water’s surface.
  4. Supplement aeration with a water pump. Aeration adds oxygen to the water by churning it. Plants, waterfalls, and fountains all help, but you can also add an aeration pump to keep the water mixed, preventing algae and odors.[8]
    • Install small pumps by attaching the water recirculating hose and placing the pump in the water away from dirt, such as on a block or rocks. Hide the open end of the hose away from the pump near some rocks. Plug the pump’s power cord into an outlet, making sure it is away from water. You may wish to bury the cord underground in PVC pipe.[9]
  5. Control the amount of food for fish. Uneaten fish food leaves nutrients that cause algae buildup. Either use higher-quality food or rely on natural food such as the algae growing on the pond liner. Don’t offer extra food when it isn’t needed. Monitor the water for leftover food and offer less as needed.[10]
    • Feed fish high-protein fish food, such as Pond Care Summer Staple, two to four times a day when the water is warm. Feed them once every day or two days with a low protein food when the water goes below 60 degrees F (15.5 degrees C).
  6. Replenish bacteria in the summer. In winter, the air filter keeps bacteria alive that would otherwise die in the cold. In the summer, algae prevention can be bolstered by adding a product such as Microbe Lift. Follow the directions on the label for the correct dosage.[11]
    • Beneficial bacteria breaks down chemicals harmful to fish, such as ammonia, and food and waste nutritious to algae.

Removing Sediment from a Shrinking Pond

  1. Vacuum out debris with a pond vacuum. Pond vacuums may be found online or at home improvement stores. They have long handles and reach the bottom of the pond to remove decaying plant matter without removing water. If your pond is small or doesn’t have much debris, all you will need to do is vacuum.[12]
    • Routine pond cleaning to remove plant matter should be done once a year in spring or fall.
  2. Prepare holding tanks for pond creatures. If you need to drain the water to reach sediment collecting on the bottom, you’ll have to remove the fish and plants to avoid harming them. Set up enough glass tanks to hold all of them. Keep the tanks in a shady location. Fill them with pond water or, if the pond water is cloudy, tap water.[13]
    • Marginal plants, which live near the water’s edge, can survive out of water but must be kept shaded, as with a tarp, and damp, as with a spray bottle or hose.
  3. Begin pumping water into a large container. Utility pumps can be found at home improvement stores. Follow the owner’s manual to install them near the water. Connect them by hose to a large container that will hold the pond water, such as a tub or tank. Make the tank as large as possible to hold fish and plants too, if you plan on using this as a holding tank.[14]
  4. Remove plants as the water level drops. As water is removed from the pond, plants will be exposed. Save your plants by moving them to the holding tanks. Place aside decaying plant matter. Small pond creatures may leave the plant matter and return to the pond.[13]
    • This is a good opportunity to repot plants and divide others that have begun to take up too much space in the pond.
  5. Catch and remove fish when the water level drops. Fish will also appear as you pump. Use a net to catch the ones you can reach and drop them into holding tanks. Once the water reaches a low level, the fish will have nowhere to go and can easily be scooped up in a net.[14]
    • Placing them in a shaded holding tank containing pond water prevents stress that harms the fish.
    • Place leaf netting over the holding tanks to contain jumping fish such as koi.
  6. Scoop out plant matter. For ponds that can be managed by hand, the sludge at the bottom of the pond can be removed by sweeping with a broom and dust pan or shovel. Dispose of the waste in the trash.[14]
    • Larger ponds with dropping water levels due to sediment buildup may benefit from excavation and bulldozing by a professional.[15]
    • Dredging is an option for removing sediment without draining the water, but this requires heavy machinery and the sediment can break apart when moved.
  7. Scrub the pond liner with water. Use a scrub brush dipped in water to loosen any leftover sludge for removal. You may see carpet-like string algae covering the liner. This algae, as long as it is on the liner, protects against discolored water. The only time you should consider removing the algae on the liner is if you don’t like the way it makes your pond look. Otherwise, remove strands on the walls or water’s surface. [2]
    • Don’t use chemicals to attack algae, since this harms fish. Blast algae off rocks using a hose and pick up the string variety by hand or with a pole.
  8. Return everything to the pond. Gradually pump water back into pond, placing plants as you go. When you are finished, let the fish back into the water. For cloudy pond water you wish to replace, use rainwater if possible or tap water.[13]
    • Rainwater can be collected by placing barrels under roof downspouts and wherever else you can find runoff.[16]
    • Tap water used in the pond will be too cold for the fish, so before you release the fish, remove some water from the holding tank and replace it with some of the new water. Do this several times.[14]

Tips

  • Remove debris yearly to avoid algae growth.
  • Algae treatment can take days or weeks to fully clear. Be patient and gradually adjust dosages of chemicals.
  • For larger ponds, contact a professional for drainage and sediment removal options.

Warnings

  • Fish are very sensitive to changes in the pond, so be careful when introducing tap water or chemicals.

Sources and Citations

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