It’s time to clean out aquatic gardens

Richard C. Bogren, Gill, Daniel J.

For Release On Or After 03/08/13

By Dan Gill
LSU AgCenter Horticulturist

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

Pond cleaning is also the best time to divide and repot water and bog plants growing in containers. They grow so enthusiastically over the summer, it’s a good idea to divide them at least once a year in early spring – except Louisiana irises and calla lilies, which are best divided in late summer.

The first step in cleaning a 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, and then pump the remaining water from the pond. As the water gets low, catch any fish you missed.

After the water is pumped out, scoop out all of the gunk and lightly scrub the bottom and sides of the pond with a brush – do not use cleaners or soap. Rinse lightly and pump out the rinse water.

Next, add new water until the pond is almost full. Save room to pour back the water that held the plants and fish. This water is full of beneficial microorganisms. But you must add a dechlorinator to the new water before you replace the fish and plants if you use water from a municipal source. Don’t forget to do this because chlorine in the water can be toxic to fish.

Next, replace the submerged and floating aquatic plants along with the water they were stored in. If you have extras plants, 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 containerized water and bog plants, if needed, before you 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.

Dividing aquatic plants

Here’s how to divide aquatic plants other than water lilies growing 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. Wash 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 any new containers half to two-thirds full with heavy garden soil. One- to three-gallon black plastic containers work well. Plant each division in the middle of a pot, and add more soil to fill the pot to within about an inch of the top. The crown of the plant should be at soil level. Top off the soil with a layer of coarse gravel.

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

When dividing and repotting plants in March, you may 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 fertilize 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 containerized 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, rinse it clean and remove the rinse water. Then 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 into the pond, even if they enjoy it. Their nails can puncture the liner.

– Wear rubber-sole 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. Also, materials used to raise pots closer to the surface, such as bricks or aged concrete blocks, should not have sharp points or edges.

Many kids love to help with cleaning out a pond (remember how you loved to play in mud and water?), so think about getting them involved.

Put in some work now and enjoy a beautiful, healthy aquatic garden this summer.

Rick Bogren

2/26/2013 9:44:37 PM
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