The Evaluation on the Use of Formalin to Neutralize Ammonia in Freshwater and Saltwater and its Effect on Hybrid Catfish and Giant Tiger Prawn (Penaeus monodon Fabricius)

Abstract

Laboratory scale experiment was done to determine the dosage of formalin needed to neutralize ammonia both in freshwater and saltwater and to study the effect of this treatment method on hybrid catfish (Clarius macrocephalus X C. gariepinus) and giant tiger prawn (Penaeus monodon Fabricius). The concentrations of ammonia used in this experiment were between 0.3 and 2.0 mg-N/l. The relationships between the dosages of formalin (Y) and the concentrations of ammonia nitrogen (X) are "Y=13.6+76.3X" for freshwater, "Y=11.63+107.25X" for 20 ppt saltwater and "Y=23.9+115.0X" for 30 ppt saltwater. The neutralization of ammonia by formalin at the concentrations of ammonia of 1.5 and 2.0 mg-N/l resulted in 15.0 and 30.0% 96 hr-mortality of 2.05 g hybrid catfish and the neutralization of ammonia by formalin at the concentrations of ammonia of 1.0, 1.5 and 2.0 mg-N/l resulted in 15.0, 33.3, and 40.0% 96 hr-mortality of 1.56 g of P monodon. When chronic toxicity tests were conducted in the period of 12 weeks, declining in growth rates of tested species were observed when formalin was used to neutralize ammonia at the concentrations of ammonia >0.8 mg-N/l for hybrid catfish and >0.5 mg-N/l for P monodon. Survival rates of test animals decreased when formalin was used to neutralize ammonia at the concentrations of ammonia >1.0 mg-N/l for hybrid catfish experiment and >0.8 mg-N/l for P monodon experiment.