Landowners with farm ponds look at various options to control weeds in the pond. Another biological control option of some unwanted aquatic vegetation is the use of tilapia in the farm pond.
Tilapia consume aquatic vegetation species such as filamentous algae, duckweed and watermeal. Tilapia can be effective in controlling some species of aquatic vegetation. Their effectiveness can be reduced in ponds with a large population of bass due to intense predation.
Tilapia is a warm water species of fish. Tilapia cannot survive at water temperatures below 55 degrees. Because they are a warm water species, stocking of tilapia usually takes place mid-April or May. Recommended stocking rates for tilapia in farm ponds is 15 to 20 pounds of mixed sex adult Mozambique tilapia per surface acre. As our water temperature drops below 55 degrees in November and December, tilapia cannot tolerate these cold water temperatures.
In Texas, stocking of Mozambique tilapia does not require a permit from the Texas Parks and Wildlife Department. Blue or Nile tilapia require an exotic species permit and are not to be used for recreational pond stocking.
Tilapia are shaped much like sunfish or crappie but can be easily identified by an interrupted lateral line characteristic of the Cichlid family of fish. They are laterally compressed and deep-bodied with long dorsal fins. The forward portion of the dorsal fin is heavily spined. The main cultured species of tilapia usually can be distinguished by different banding patterns on the caudal fin. Male Mozambique tilapia also has upturned snouts. Color patterns on the body and fins also may distinguish species.
Tilapia can survive in pH ranging from 5 to 10 but do best in a pH range of 6 to 9. The pH scale measures how acidic or alkaline a soil or water may be. Agriculture limestone may need to be applied to the newly renovated pond to help change the pH of the soil or water. Applying limestone directly to the bottom of the pond is acceptable as the limestone will begin to break down as we receive rainfall. Just like pastures, farm ponds have an optimum pH level that enhances fish growth and reproduction. The pH of a farm pond should range from 6.5 to 9.0.
Total alkalinity in farm ponds should be greater than 20 parts per million. Alkalinity is a measure of bases in the water. Bases react to neutralize acids and, therefore, directly influence pH. As bases react with the hydrogen ions present, they buffer or suppress pH changes.
Proper identification of the weed species in the farm pond is important to help determine a plan of action when choosing various control methods. A helpful website to do this is http://aquaplant.tamu.edu . This website shows photos of weeds offering biological, mechanical and chemical control of aquatic vegetation.
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