Pond Management

By Scott Williams and Andrew Branson | May 1, 2020
From Missouri Conservationist: May 2020

Pond owners sometimes have a love-hate relationship with their ponds. People want a beautiful pond that looks nice, attracts wildlife, and provides great fishing. However, depending on the circumstances, these wants may be hard to achieve.

Ponds are very much like a living thing. They change with age, what you put into them can have a dramatic effect over time, and problems can be difficult and expensive to fix. Like a person’s health, the health of a pond can be improved and maintained by taking steps to protect it.

Pond Turnover

Unless it is very shallow, all ponds in Missouri turn over twice a year. Turnovers occur in the spring and again in the fall as temperatures cool. Ponds in Missouri stratify, meaning they have layers of water at different temperatures that do not readily mix. In the summer, most ponds have a cool layer of water near the bottom and a warm layer of water near the surface. If you have ever enjoyed a summertime swim in a pond, you have probably felt this phenomenon as your feet were in much cooler water than the rest of you. As air temperatures cool in the fall, the temperature of the upper layer of water cools and as it nears the temperature of the lower layer of water, the two layers slowly mix. As long as this process occurs slowly, there are no problems for the pond. However, if the turnover happens quickly, due to severe weather, the gasses trapped in the lower layer are released too quickly and the dissolved oxygen in the pond can be used up, resulting in a fish kill.

As winter temperatures drop, the pond will form a cold layer of water on the surface, and a warmer layer of water near the bottom. As spring arrives and warms the upper layer of water to match the lower layer, the turnover process occurs again.

Water is a fascinating compound that does not follow the rules of most other compounds. Most things are their most dense in a solid state, but not water. Water is most dense at about 39 degrees, which is why water at or below 32 degrees turns into ice and floats. The density of cold water makes it very reluctant to mix with water of a warmer temperature, and this allows the process of stratification to occur. If water didn’t behave differently than most compounds and was most dense at a solid state (ice), we would not enjoy all the fish that we have in areas that experience freezing temperatures. This is because as ice formed, it would sink to the bottom and slowly fill the entire water body with ice and there would be no place for fish to survive.

Grass Carp

Grass carp can be a good addition to a pond when needed and stocked appropriately. Grass carp should only be stocked in a pond that is having a problem with too much nuisance aquatic plants, and if those plants are the type that grass carp will eat.

Some common aquatic plants eaten by grass carp:

  • Pondweed, Potemogeton, Najas
  • Milfoil, Myriophyllum
  • Coontail, Ceratophyllum
  • Waterweed, Elodea
  • Muskgrass, Chara
  • Cattail, Typha spp.
  • Water lilies, Nymphaea odorata

Grass carp should not be stocked when a pond is not having plant problems. Grass carp are long-lived and difficult to remove once stocked, so only add them when necessary.

Consider other possible options to control aquatic plants such as shading, winter draw down of the pond water, or herbicide application. Many times, it helps to use a couple different methods of aquatic plant control.

Suggested grass carp stocking rates:

  • 10–20 percent, mechanical or chemical spot treatment
  • 20–40 percent, 2–5 carp
  • 40–60 percent, 5–10 carp
  • over 60 percent, 10–20 carp

Stock grass carp that are 8–12 inches in length to avoid being eaten by bass, and give the stocked fish at least two years to start getting ahead of the plant growth. Using a secondary control technique will help the grass carp be more effective at controlling vegetation in a shorter time frame.

Note: Grass carp can eat beneficial aquatic plants in addition to the nuisance ones. Do not add more than the recommended number for your situation.

Detailed descriptions of these control methods can be found at mdc.mo.gov, or by contacting your local MDC office.

Good Quality Pond

Pond Location

The pond is located on an appropriate site. The soils are correct for holding water, the dam is constructed properly, and the pond received an adequate amount of water from its watershed to keep it full, but not so much as to constantly flush it out.

Fish Structure

Brush piles can be a great benefit to fish in a pond. Large piles of cedar trees or
hardwood tree tops placed in 8 feet of water or less will attract and hold fish, give small fish a place to find cover, and attract aquatic insects and other food sources for your fish.


This may come as a surprise to some, but harvesting the appropriate amount of different types of fish is very important to maintaining the balance of the fish population and attaining maximum fish growth.

Well-Maintained Dam

A well-maintained dam will improve the lifespan and health of a pond. Good dam maintenance requires periodic mowing to prevent the establishment of woody vegetation, such as trees. Trees can root through a dam and can cause leaks or other structural problems. If your pond dam has trees on it, only remove the trees that have a trunk diameter of 4 inches or less. Cutting larger trees can increase the chances for leaks.

Quality Water Source

The watershed, or land area from which a pond gets its water, is covered with vegetation (trees are best, but grass works, too). The pond is fenced from livestock to reduce damage to its banks and direct inputs of nutrients through manure. If livestock are present in the watershed, the pond has at least a 100-foot border of vegetation to filter nutrients before they get to the pond.

Aquatic Plants

Fifteen to 25 percent of the pond bottom has rooted aquatic plants. Not all types of aquatic plants are created equal. Plants like pickerel weed, spatterdock, and arrowhead provide cover and a place to find food for fish without taking over.

Fish Stocking

In small ponds, a combination of largemouth bass, bluegill, and channel catfish work well. If you stick to these types of fish, and stock according to the rates recommended for your area, you will have the best chance of producing a balanced, healthy fish population.

Missouri Pond Handbook is available free for Missouri residents. Order a copy from pubstaff@mdc.mo.gov or by calling 573-522-0108. Provide the publication title and your shipping address.

Poor Quality Pond

Too Many Nutrients

Nitrogen and phosphorus from livestock and lawn fertilizers can cause excessive growths of algae. Algal blooms in the summer can make your pond look uninviting and can even cause fish kills.

Nuisance Aquatic Plants

Aquatic plants are good, but too many are a problem. They make it impossible to fish, difficult for larger fish to get to smaller fish for food, and susceptible to fish kills. Control nuisance aquatic plants by removing them, using aquatic approved herbicides, or stocking
grass carp. Identify the type of vegetation present to determine the best course of action to control it. Nuisance vegetation can be controlled in the long term by limiting nutrient inputs and planting good quality aquatic vegetation to use available nutrients.

Lots of Small Bass

Many pond owners complain that the largemouth bass in their pond are all small. This is normally caused by under harvest of bass. To get your bass under control and help increase their size, start harvesting the bass that are under 12 inches long at a rate of 35 bass/acre/year. While you are doing this, protect your bluegill from harvest for a couple years so they can spawn and provide more food for the bass. After a couple years, reduce your bass harvest to 25 bass/acre/year and maintain it at that level. Keeping harvest records makes this job easier. Bass may also exhibit poor growth if there is too much dense aquatic plants in the pond and they cannot catch an adequate amount of food. If this is the case, take steps to decrease the amount of vegetation in the pond.

Inappropriate Fish

Avoid stocking blue and flathead catfish, common carp, and goldfish. Also, bullhead catfish are poorly suited for a pond and can even cause damage. Another fish that everyone loves, but are not the best suited fish for smaller ponds, are crappie. Crappie can quickly overpopulate in a pond and exhibit poor growth and small size. Too many crappie can also harm the growth of other types of fish in the pond.

Also In This Issue

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This Issue's Staff

Magazine Manager - Stephanie Thurber

Editor - Angie Daly Morfeld

Associate Editor - Larry Archer

Staff Writer - Bonnie Chasteen
Staff Writer - Heather Feeler
Staff Writer - Kristie Hilgedick
Staff Writer - Joe Jerek

Art Director - Cliff White

Designer - Shawn Carey
Designer - Les Fortenberry
Designer - Marci Porter

Photographer - Noppadol Paothong
Photographer - David Stonner

Circulation - Laura Scheuler