Chlorination of channel catfish ponds

Abstract

Laboratory studies with pond water samples revealed that 5 mg/L active chlorine was needed to provide enough chlorine residual to reduce biological activity. Treatment of channel catfish ponds with repeated, 0.1-mg/L doses of active chlorine from calcium hypochlorite at 6-to 8-d intervals, as sometimes done by catfish farmers, had little influence on water quality. Dissolved oxygen, total ammonia-nitrogen, and chlorophyll a concentrations and pH were similar between treated and control ponds. Concentrations of chemical oxygen demand and particulate organic matter were seldom different between treated and control ponds. Channel catfish survival and net production were not improved by chlorine treatment. Thus, chlorination of production ponds during the grow-out period is not a useful technique. Treatment of sediment samples from ponds with up to 1,200-mg active chlorine/kg soil did not reduce bacterial abundance, so chlorination of bottoms of empty ponds may not be an effective disinfection procedure. Chlorination of pond waters with 30-mg/L active chlorine caused complete kill of bacteria 24 h after treatment, although heterotrophic bacteria quickly repopulated the water. Thus, chlorination can be an effective way to disinfect ponds before stocking.