Chanagun Chitmanat, Kitiwan Tongdonmuan, and Wichan Nunsong

pp. 359 - 364

Abstract

The treatment for ectoparasitic diseases in freshwater fish with formalin seems at present to be ineffective. For this reason it is evidently a useless cost. In addition, formalin possibly leaves toxic residues in fish
flesh and in the environment which are eventually harmful to consumers. The alternative way to solve this
problem is to use traditional medicinal plants instead. The purpose of this research is to determine the possibility of using garlic (Allium sativum) and Indian almond (Terminalia catappa) as optional chemicals to treat
fish ectoparasites, Trichodina sp. The results showed that crude extracts of either garlic or Indian almond at
800 mg/l significantly (P < 0.05) eliminated Trichodina sp. infections in tilapia (average weight 3.62±0.06 g
each). To evaluate the acute toxicity of these products to the host fish, groups of 20 tilapia (same size as above)
were exposed to 3 concentrations of each product for 96 h. Mortality was then determined. The 2 h LC₅₀ for
tilapia exposed to crude extract of garlic was 2,259.44 mg/L while the 16 h LC₅₀ for tilapia exposed to Indian
almond extract was 46,665.94 mg/L. This information is the beneficial and fundamental knowledge to develop
guidelines to reduce the use of chemicals and antibiotics in freshwater fish culture businesses. The research is
underway to determine the long-term effect of Indian almond and garlic to tilapia, if any.