Water management

Fish farms require large volumes of good quality water. The water required for levee ponds can be estimated as either a minimum of 13 gallons per minute of flow for each surface acre of pond or 3 times the pond volume per year. When considering other sources, such as streams and watershed reservoirs, get the advice of a Soil engineer (If you can find one). Wells or springs are the preferred source of water for catfish ponds. Run well and spring water over screening or splash boards to increase oxygen content. Water from streams and lakes must be screened to keep out wild fish, which would otherwise reproduce and compete with the catfish for feed and space.

It is not practical to analyze every possible water quality variable and contaminant that might make water unfit for fish farming. The best way to evaluate water is to grow a few catfish in an aquarium filled with the water or in a cage suspended in the water. Laboratory tests for total alkalinity, total hardness, total iron, nitrate and salinity can also be useful. Table 1 gives recommended ranges for these water quality variables. Seek further advice if water quality values are outside of the recommended range. Situations to avoid in selecting a water source include:

1. Surface water sources subject to pesticide pollution. Streams and lakes bordering agricultural land may receive pesticides in the form of runoff or spray drift.

2. Deep wells or other water sources with high pumping costs. Estimate annual pumping costs before committing yourself to use a water source.

3. Watershed impoundments that are too fertile. A heavy growth of microscopic plants (phytoplankton) giving water a dense green or brown color is an indication of this problem. Fish kills due to low oxygen are more likely in such water.

The key to maintaining good water quality is to measure the surface acreage of each pond exactly and not stock more than the recommended number of fish per surface acre. Extra fish mean extra nutrients going into the pond in the form of feed. This leads to heavy growth of microscopic plants (phytoplankton) which die and decay leading to lack of oxygen and sudden large fish kills. To maintain water quality over the long term, many farmers drain their ponds every 5 to 10 years, allow them to dry and then scrape out the organic material that has built up on the bottom.