Research & Article

The toxicity of detergents to giant freshwater prawns varied considerably according to the hardness of the water in which the prawns were treated. The 96-h LC50 (96-hour median lethal concentration) values of soft detergent were, respectively, 21.9, 18.2 and 18.1 mg/I in soft, moderate and hard waters, whereas the 96-h LC50 values of hard detergent were, respectively, 61.7, 54.7 and 54.4 mg/1 in soft, moderate and hard waters. The detergent was more toxic in hard water than in soft water. Increasing water temperature increased considerably the toxicity of detergent to prawns. At 23 , 28* and 33*C, the 96-h LC50. values of soft detergent were, respectively, 20.9, 18.2 and 11.8 mg/, and of hard detergent were, respectively, 59.5, 54.7 and 41.3 mg/l.