Taking Care of Weeds in Farm Ponds

May 23, 2017 - I’ve said many times here and to folks across the county that I get more questions specifically about pond management than any other topic. Indeed, a staple of east Texas land owners is the farm pond.

Ponds can serve many purposes. Well-managed ponds can provide irrigation, an easily-accessible water source for livestock and can be tremendous wildlife habitat. Primarily, many ponds are used for recreational activities such as boating, swimming and most often, fishing.

And when you break up the pond questions into categories, getting rid of excess vegetation is at the top of that list.

Before we start, please understand that some vegetation is good and even needed in most ponds. Vegetation provides cover and helps add oxygen. Interestingly, too much vegetation can lead to problems as well.

There are four kinds of aquatic vegetation: submersed (completely underwater), immersed (with dry vegetative matter existing above the surface), floating vegetation, and algae. In local terms, these pond weeds are either all below the water, above the water, float on top, or pond scum.

There are two commonly used types of control – plant-eating fish or herbicides. The two types of fish that can be used to control pond weeds: grass carp and tilapia.

Grass carp are state restricted fish requiring a permit from the Texas Parks and Wildlife. Grass carp do an excellent job of consuming weeds such as elodea, hydrilla, naiads, pondweed, chara, and parrotfeather. You can request an application for a grass carp permit by calling your local Texas Parks and Wildlife office.

Tilapia is a tropical, freshwater fish that are excellent at controlling algae, mosquito fern, bladder wort, duck weed, and water meal. Tilapia are not restricted but, due to their tropical nature, die off during the winter in un-heated water and need to be thought of as an annual biological treatment. In ponds large enough to include bass, the tilapia help fatten up bass for the winter months as tilapia get sluggish in cooling water.

My most recent calls have been about filamentous algae. We’ve got lots of not-so-flattering colloquial names such as “slime” and “pond scum”. Filamentous algae is the slimy material you have to remove from the fish hook each time.

Controlling this algae can be done fairly easily with the above mentioned tilapia and with several available products that contain copper. Copper products including copper sulfate, bluestone, Cutrine, Komeen, and many others.

I mention algae not only because those are the most recent questions, but because it is common, easy to control and can cause problems most quickly.

Herbicides approved for use in ponds will not kill fish. However, when something is killed and begins to rot, the decomposition process consumes oxygen. A dead squirrel on the side of the road may not cause any serious lack of oxygen, but a pond full of decomposing vegetation certainly can result in a fish die-off from lack of oxygen.

A possible solution to the oxygen depletion problem and subsequent die-off of fish is to treat no more than a third of the pond at a time so that fish have oxygen available.

Let if be said, there are products commonly used in ponds that have no business there. If the label does not state that it can be used in a pond with specific instructions on how to apply it, then it is not legal to use in a pond.

With the bevy of products available, there is not enough room in this article to cover them all. Contact the Extension office for exactly which products to use with your circumstance.

Submitted by Lane Dunn
County Extension Agent-Shelby County
Agriculture and Natural Resources