A very popular water preparation agent, used especially for preventive treatment of fish, for instance after transport, after water changes, during feeding with plankton etc. In lower concentrations (very light colouration of water), it may be used to treat spawn of problematic fish. It is recommended always to use METHYLENE BLUE to treat freshly imported fish, weak fish or fish with apparent respiratory problems. This agent is suitable for the removal of moulds, parasites and initial stages of bacterial infections. It has an oxidizing effect.