WATER QUALITY includes all physical, chemical, and biological factors that influence the beneficial use of water. Where aquaculture is concerned, any characteristic of water that affects the survival, reproduction, growth, or management of fish or other aquatic creatures in any way is a water quality variable. There are many water quality variables in pond aquaculture, but only a few of these normally play an important role. These are the variables that aquaculturists should attempt to control by management techniques. All other things being equal, a pond with "good" water quality will produce more and healthier aquatic creatures than a pond with "poor" water quality. A knowledge of water quality principles will help the aquaculturists in determining the potential of a body of water for aquaculture, improving environmental conditions in ponds, avoiding stress-related diseases and parasite problems, and ultimately producing aquatic creatures more efficiently.
Scientific papers and books on water quality dynamics and management in ponds are quite technical and detailed. Therefore, Boyd and Lichthopper (6) prepared a simple and concise manual of the major aspects of pond water quality and its management for practical aquaculturists. That publication was popular, but it is now out of print. This manual is a revision of the manual by Boyd and Lichtkoppler. It covers the major water quality variables, including salinity, pH and alkalinity, dissolved oxygen, plankton, nutrients, and toxic metabolites. It explains how these variables relate to the use of fertilizers and feeds to increase production in ponds. It also discusses the improvement of water quality through mechanical aeration and other methods. This manual explains only the usual relationships between water quality variables and aquacultural production and provides some common management methods. All aspects of pond water quality and its management cannot be covered in a small manual or in a simplistic way. Those wanting a more complete account of water quality may consult Boyd ( 2 ) or Boyd and Tucker (7).