Managing issues with your pond

Jim Crawford, Field Specialist in Agricultural Engineering University of Missouri Extension

Missouri is proud to be known as a “Pond State.” According to the Missouri Department of Conservation, there are over 300,000 privately-owned ponds and lakes in the state. These ponds provide water for people, livestock and wild animals as well as habitat and food for numerous fish, birds and other aquatic animals.

As spring turns into summer, ponds undergo many changes – some good and some not so good. Most pond owners take pride in their ponds so these changes are a cause for concern. The best way to avoid issues is with good maintenance and operational plan for your pond. But that is not always possible. Below I will briefly describe some of the issues you may experience with your pond as well as some solutions.

One of the first changes people notice are “weeds” covering the pond. The first step is to correctly identify the material in your pond. Is it a floating weed? Is it anchored to the bottom? Is it a plant or algae? Proper identification is critical in order to develop the proper strategy for control.

While there are several maintenance, mechanical and biological controls available, generally by the time people recognize an issue, these methods will not be effective leaving to the last resort of chemicals. When chemicals are used to control weeds, it is critical you read and follow the label. As dead plants break down, they use oxygen from the water. To avoid oxygen depletion and a possible fish kill, avoid treating when the water temperature is above 80 degrees Fahrenheit and treat only 1/4 of the vegetation at a time.

Filamentous green algae, often referred to as pond scum, is one of the most common issues with ponds. They form dense mats floating on the surface and have no leaves or stems. Algae are important for healthy rivers, streams, ponds, and lakes, and all the human interests that involve water, including boating and fishing. However, when filamentous algae flourishes, it can impede fishing and swimming, clog water intake screens and hurt the ecology, as well as the visual aesthetics, of a pond. Products containing copper sulfate provide effective control of algae.

Often confused with algae, duckweeds are the smallest of the flowering plants. They consist of tiny, green, rounded, leaflike bodies that float on the water’s surface. Several duckweed plants can fit easily on a fingertip. Missouri has 8 species of duckweeds, 2 of giant duckweed, and 3 of watermeal. Each duckweed plant is less than 1/4 inch across with a single short, hairlike root that dangles into the water. While a benefit to wildlife, in nutrient-rich pond duckweed can spread quickly, cover the surface, and become a nuisance. Products containing Carfentrazone,

Flumioxazin, or Penoxsulam provide good control.

Another common plant found around ponds are cattails. Cattails are tall plants with narrow, upright leaves with a central stalk bearing a brown, sausage-shaped flower spike. The brown section consists of female flowers while above it on the stalk, the male flowers are yellow. Unlike algae and duckweed, they grow in shallow, stagnate or slow-moving water from rhizomes in the soil. They grow rapidly with a tendency to collect soil around their roots. This captured soil can fill in shallow ponds and other wet areas. They can become invasive and displace other

wetland vegetation. Products with the active an active ingredient of Glyphosate, Imazamox or Imazapyr will control cattails.

The water level in all ponds will drop throughout the course of the year (even those without a leak) due to evaporation, seepage and usage by people, plants and animals. Many years, rainfall is not adequate to keep up with these removals and the water level will drop.

When the water level drops, it is not necessarily due to a leak. Seepage is water lost through the soil and is normal. A well-constructed pond can lose up to an inch of water per month due to seepage. However, if the water level is dropping faster than this it could be a good indicator of a leak. Wet spots, seeps or the growth of aquatic vegetation outside the pond can also indicate a leak. Dropping water levels are a call I hate to answer – because there is generally not a good answer to stop it. The most common, and best way, to solve a leak is reconstruction of the pond – which is both expensive and time consuming.

These are just 4 of the most common issues that I hear regarding ponds. The Missouri Department of Conservation maintains an excellent webpage on ponds containing information on the constructions, operations, maintenance and solutions for most pond issues. This is my go-to source for information on ponds.