How to keep your pond healthy by Mario Villarino

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Ponds located across the state have different water chemistry, caused by factors such as soil type, water sources, and watershed characteristics.

The water chemistry in a pond affects primary productivity which determines the number of fish to stock as well as the pond’s fish carrying capacity. One characteristic that controls the ability of a pond to produce fish is alkalinity.

Alkalinity is the measure of buffering capacity, and is commonly described as milligrams per liter or
parts per million calcium carbonate (mg/L or ppm CaCO3). A total alkalinity of at least 20 ppm is
required for good pond productivity.

Ponds located within pine-forested watersheds are especially susceptible to low alkalinity. In ponds with low alkalinity, pH can vary widely throughout the course of the day, causing unnecessary stress on fish populations. In this situation, it is often difficult to establish a phytoplankton bloom, which is the base of the pond’s food chain.

If you plan to fertilize, you should have the alkalinity checked. If alkalinity is less than 20 ppm and you want to fertilize, agricultural lime can be added to increase alkalinity. Do NOT use hydrated or quick lime, as rapid pH changes could cause a fish kill.

Agricultural lime is often available in bulk quantities and can be delivered to your site. Common
application rates range from one to four tons per surface acre. The lime should be applied as
uniformly as possible over the surface of the pond to ensure coverage.

Distributing the lime from a plywood platform on the front of a boat is a common application method. Check with local authorities or review the information found in the accompanying references to decide if liming is something you need
to consider.

For more information on this or any other agricultural topic please contact the Hopkins County Extension Office at 903-885-3443 or email m-villarino@tamu.edu.

By Mario Villarino

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