Description

Abstract: Growing Clarias spp. using prepared feeds is a common practice in Thailand. Usually Clarias are grown in circulating systems such as concrete tanks flushed with water from a reservoir or earthen ponds without water replacement. Because of their ability to breathe air, Clarias can tolerate low levels of oxygen in the water of these rearing systems; however, water quality does appear to influence growth and survival (Diana et al., 1988). Water quality in circulating systems can be improved by the following methods: 1) flushing, 2) lowering stocking density in tanks, or 3) lowering feeding rates. An alternative to the above mentioned methods involves the utilization of a system that combines Clarias in cages with tilapia at large, and allows primary production in the pond waters to utilize surplus nutrients. The tilapia may harvest phytoplankton as food to further improve water quality. In addition to tilapia, silver carp and/or other phytoplanktivores are also believed to reduce phytoplankton abundance. This system combines a fed, growout pond and settling pond into one system with the harvest of two crops.