It’s time to clean out aquatic gardens

Richard Bogren, Young, John, Gill, Daniel J., Owings, Allen D.

News Release Distributed 03/19/10

By LSU AgCenter Horticulturists Dan Gill, Allen Owings and John Young

Aquatic gardens and water features are important parts of sustainable landscapes. Water provides for the needs of birds and other wildlife that live in our yards. The sight and sound of water also add to the overall beauty and enjoyment of our yards and gardens.

Most aquatic gardens are made by excavating the soil and lining the hole with pond liner, or they’re created in large, waterproof containers. The following information is appropriate for these installations but not for large ponds with soil bottoms.

If the bottom of your pond or aquatic garden has a thick layer of gunk, it’s a good idea to clean it out this month. Generally, you should clean out smaller aquatic gardens about once a year and larger ones every few years. It’s best to get this done while the weather is cool, the plants are relatively dormant and the fish are less active.

Cleaning a pond also is the best time to divide and repot water and bog plants growing in containers. They grow so enthusiastically over the summer, it is a good idea to divide them at least once a year. Louisiana iris and calla lilies, however, should be divided in September.

The first step in cleaning out the pond is to remove all of the fish and plants. Put fish and submerged and floating plants in separate buckets or tubs filled with water from the pond, then pump the water out of the pond. As the water gets low, you can catch any fish you missed. When the water is pumped out, scoop out all of the gunk and lightly scrub the bottom and sides of the pond with a brush – but do not use cleaners or soap. Rinse the liner lightly and pump out the rinse water.

Then, add new water until the pond is almost full. Save room to pour in the water you have with the plants and fish. This water is full of beneficial microorganisms. If you filled your pond from a public source, you must add dechlorinator to the water before you replace the fish and plants. Don’t forget to do this because chlorine in the water can be toxic to fish and plants.

Next, put back the submerged plants and floating aquatic plants and the water they were stored in. If you have extras, put them in your compost. Never put aquatic plants into natural ponds, streams or lakes where their excessive growth could become a problem. Trim, divide and repot potted water and bog plants as needed – except Louisiana iris and calla lilies, which are in active growth now – and place them back into the pond.

Finally, put fish in plastic bags filled with water from the bucket or tub they were held in, seal them shut (with zipper or wire twist) and float the bags in the pond for about 15 minutes or until the water in the bag and the water in the pond are the same temperature. Then release the fish.

Here’s how to divide aquatic plants – other than water lilies – that grow in containers. First, take the plant out of the pond and remove it from the pot. If it is very pot bound, you may have to cut the plastic pot to free the plant. Hose off the soil to reveal the root and rhizome structure of the plant, then use a large knife to cut the plant into two to four pieces.

Next, fill a container half to two-thirds full of heavy garden soil – 1- to 3-gallon black plastic containers work well. Place the plant division in the middle of the pot and add more soil to fill the pot within about an inch of the top. The crown of the plant should be at soil level. Top off the pot with a layer of coarse gravel.

Finally, water the pot to saturate the soil and gently place the pot in the pond. The rim of the pot should be no more that 2 to 4 inches below the soil surface. Place the pot on bricks or other materials if necessary.

When dividing and repotting plants in March, you may or may not need to add aquatic plant fertilizer tablets. If the plants are showing signs of growth, put the appropriate number of tablets in each pot according to the manufacturer’s directions. Otherwise, you can wait to fertilizer until new growth begins.

Even if you decide not to clean out your pond and divide plants this month, at least trim off all dead, brown, freeze-damaged leaves and stems from floating and potted aquatic plants. That way, the healthy new growth does not get mixed into the old, unattractive foliage.

If your pond liner has been leaking, it should be repaired during the pond cleaning process. When all of the water is out of the pond and the liner has been scrubbed and rinsed clean and the rinse water removed, dry the liner and locate the leak. Patch kits are available where you purchased your liner and should be used according to directions to repair the leak.

To avoid damaging the liner in the future, keep these points in mind:

– Never allow dogs in a pond, even if they enjoy it. Their nails can puncture the liner.

– Wear rubber-soled sneakers when walking in the pond. \

– Make sure tools, such as skimmer nets, do not have sharp edges or points that might damage the liner.

– Make sure materials used to raise pots closer to the surface, such as bricks or aged concrete blocks, don’t have sharp points or edges.

Visit LaHouse in Baton Rouge to see sustainable landscape practices in action. The home and landscape resource center is near the intersection of Burbank Drive and Nicholson Drive (Louisiana Highway 30) in Baton Rouge, across the street from the LSU baseball stadium. For more information, go to and

Rick Bogren

1/4/2011 1:07:30 AM
Rate This Article:

Have a question or comment about the information on this page?

Innovate . Educate . Improve Lives

The LSU AgCenter and the LSU College of Agriculture