This document discusses the various chemicals used in aquaculture for disease control, increased production, and improved animal welfare. It outlines common disinfectants like hypochlorite, quaternary ammonium compounds, and EDTA. It also discusses feed additives and therapeutants like sulfonamides, terramycin, formalin, potassium permanganate, NaCl, and copper sulfate that are applied to water for disease treatment. Many of these chemicals are effective against bacteria and parasites but require proper dosing to avoid toxicity.