How to Clean an Outdoor Pond

If your pond has the correct fish-to-plant ratio and is sited so that leaves and other debris are not blown into the water, you probably won't need to clean your pond. However, most of us have ponds that are located near deciduous trees and shrubs; we happily add way too many koi, carp and goldfish; and we don't prune and care for the aquatic plants the way we should. So, every fall, we must clean out our ponds to keep them healthy and to prevent winter fish kill. You can make the yearly pond cleaning easier by skimming leaves, branches and other debris from the surface of the pond every day or at least once a month. Cleaning your pond removes rotting vegetation that encourages algae bloom and pests that could harm your fish and plants, and it gives you a chance to divide your aquatic plants as well as add some new ones.

Things You'll Need

• Rubber gloves and boots
• Garden hose with spray nozzle
• Medium-sized kiddie pool at least 3 feet deep or 100-gallon rubber stock tank
• Buckets
• Fish net
• Air stone or large aquarium pump
• Spade
• Pool skimmer
• Wet/dry vacuum
• Pliers
• Spare parts for your filter
• Pruning shears or scissors
• Dechlorination tablets
• Thermometer
• Water heater

Instructions

1. Choose a slightly overcast day in early fall with temperatures above 60 degrees F to clean your pond.

2. Set up a holding tank for your fish by filling a kiddie pool that is at least 3 feet deep or a 100-gallon rubber stock tank with water from your pond. You can use buckets or siphon water from the pond to the holding tank using your garden hose. Place the holding tank in a shady spot.

3. Begin draining water from your pond by either setting your filter valve to the "drain" position or re-routing the hose from your filter to drain outside the pond rather than recirculating the water. Stop when your pond is half empty.

4. Fill your buckets with pond water. As you catch the fish, place them in the filled buckets for transfer to the holding tanks.

5. Set up air stones or a large aquarium pump to oxygenate the water in the holding tanks.

6. Transfer plants that float on the surface of the pond (such as water lettuce and duckweed) to your holding tanks.

7. Finish draining your pond, removing as much water as possible. Turn your filter off when you are through draining water.

8. Remove as many plants from the pond as you can. Leave in place cattails and other aquatic plants that form large clumps.

9. Use your pool skimmer to go through the muck on the bottom of the pond. Remove snails, dragonfly larva, tadpoles and frogs from the bottom and transfer to a bucket filled with pond water.

10. Use the spray function on your garden hose nozzle to pressure wash the sides of your pond liner and any large rocks.

11. Vacuum the muck from the bottom of your pond. Stir up the stones, gravel or pebbles on the bottom to get as much muck as possible.

12. Remove your filter and take it apart. Wash the individual parts, removing algae and other contaminants that are adhering to the parts. Replace any worn or broken pieces. Reassemble the filter and set it back up in the pond.

13. Gently wash algae and insects or snails off the plants you removed from the water. If the crown is dying back, divide the plants. You can either give away, replant or compost the divisions. Remove dead or dying leaves. Replant in the pond, taking care not to crowd them. If large clumping plants like cattails are taking over, pull up 1/2 of the clump, starting at the edges and working inward.

14. Refill your pond with water. Add dechlorination tablets if you are using city or county water. Turn on your pond's filter as soon as it is covered with water.

15. Place a water heater in your pond to warm the water to within 10 degrees of the water temperature in the holding tanks.

16. Place your fish, snails, tadpoles and other animals in the pond when the water has warmed up. Replace your floating plants at this time.

Tips & Warnings

• If you live in an area that is susceptible to drought, save the pond water and use it to water your flowers or shrubs. Do not use pond water to water veggies or plants that you might consume. Compost the muck you remove from the bottom of your pond. If you have a small pond with no fish, you probably won't need to clean it, unless the water is green or excessively murky.

• Remove fish when cleaning ponds, as the sediment that is stirred up during the cleaning can deplete oxygen from the water, causing them to suffocate.