Toxicity of formalin on behaviour and respiration in Danio rerio

Formalin is an effective chemotherapeutic agent for combating several infectious conditions affecting fish of aquacultural importance and ornamental fish. It is applied as bath, flush or flowing treatment method and has proved to be effective against a variety of fish parasites and microbes. The toxicity of formalin on the behavior and respiration of the popular aquarium Zebra fish Danio rerio was evaluated 96 hour LC50 value was found to be 30ppm. Abnormal behavior and swimming movements, reduced opercular beats, increased mucus secretion and mortality were recorded due to formalin toxicity on zebrafish. Oxygen consumption of zebrafish exposed to sub-lethal concentration of formalin showed a time dependent decrease with 62.4% reduction at the end of 96 hours. The need for judicious use of fish chemotherapeutants like formalin and their impact on fish life are discussed.