Replace 3/4 of the aquarium water prior to beginning treatment with dactymor. Add 5 ml (= 100 drops) of dactymor for every 100 l of aquarium water and stir the aquarium water to disperse the product. Switch off UV-lamps. After 6 hours treatment a replacement of minimum 3/4 of the aquarium water is required. On the following day change half of the aquarium water. A single treatment is generally adequate for skin worms and tapeworms. However, trematode eggs are not affected. Therefore, when treating trematodes, the treatment should be repeated twice, waiting approx. one week between each treatment (for coldwater ornamental fish, wait approx. one-and-one-half weeks between treatments).The aquarium should be continuously monitored during the treatment with dactymor. In aquariums containing a large biomass (microorganisms in filters, ground, etc.) the use of dactymor may result in an increase in bacterial growth. In turn this can lead to an oxygen depletion. Immediately change the aquarium water if signs of bacterial turbidity or indications of oxygen depletion are observed.