Five different solvents namely Petroleum
ether, Dichloromethane, Chloroform, ethanol and water were used. The bioactive compounds present in
the extracts showed antioxidant and antibacterial activities against Aeromonas salmonicida. Ethanol and aqueous
extracts of these seaweeds were found to have better antibacterial activity against bacterial diseases in fish when
compared to the other extracts. Toxicological and in vivo pathogenicity studies were performed with the highest
concentration of 250 mg/l of extracts. The compounds identified by GC–MS which were found to have antibacterial
activity were prepared in the form of a colloidal suspension for oral treatment. The use of algal extracts in
aquaculture disease management is a cost effective and eco-friendly approach. These extracts could be used as
prophylactics.