Now Is Time To Clean Out Your Aquatic Garden – If Needed

Daniel Gill, Merrill, Thomas A.  |  4/22/2005 12:36:30 AM

Get It Growing News For 03/25/05

By Dan Gill
LSU AgCenter Horticulturist

It’s time to decide if your aquatic garden could use a good cleaning, since now is the best time to accomplish that task.

If there is a thick layer of gunk on the bottom of your pond or aquatic garden, it is a good idea to clean it out during March or early April – while the weather is cool, the plants are relatively dormant and the fish are less active.

Generally, you should clean out smaller aquatic gardens about once a year and larger ones every few years.

Pond cleaning time also is the best time to divide and repot water and bog plants growing in containers. They grow so enthusiastically over the summer that it is 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 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 out the water from the pond.

As the water gets low, catch any fish you missed. When the water has been 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 lightly and pump out the rinse water.

Next, add new water until the pond is almost full. Save room to pour the water you have the plants and fish in back into the pond. It is full of beneficial microorganisms.

Remember, you must add a dechlorinator to the water before you replace the fish and plants if you use water from a municipal source. Do not forget to do this, since chlorine in the water can be toxic to the fish!

Then put the submerged plants and floating aquatic plants and the water they were stored in back into the pond. 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 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

If your aquatic plants need to be divided, 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. 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. One- to 3-gallon black plastic containers work well. Plant the 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 plants should be at soil level. Top off 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 than 2-4 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 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 based on the fertilizer manufacturer’s directions. Otherwise, you can wait until new growth begins to fertilize.

Other Tips

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.

In addition, 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, rinsed clean and the rinse water removed, dry the liner and locate the leak. Patch kits generally are available at stores where liners are sold 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 your dog into the pond, even if he enjoys it. Its 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.

–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 the pond (Remember how you loved to play in mud and water?), so think about getting them involved.

At any rate, put in some work now and enjoy a beautiful, healthy aquatic garden this summer.

Get It Growing is a weekly feature on home lawn and garden topics prepared by experts in the LSU AgCenter. For more information on such topics, contact your parish LSU AgCenter Extension office or visit our Web site at A wide range of publications and a variety of other resources are available.


Contact:     Dan Gill at (225) 578-2222 or
Editor:        Tom Merrill at (225) 578-2263 or

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