Read all instructions carefully before using - 1 drop for every 4 liters or 1 gallon. The dropper contains approx. 300 drops (10 ml). The dropper cap holds approx. 90 drops. So 1 cap full is good for 360 liters or 90 gallons. Add it in a high flow area of the tank. If you want to treat a refugium only and if it’s volume is too small for using a powerhead then mixing should be done manually. - It should start to work within 30 minutes. - If within 45 minutes no visible death of flatworms occurs add 50% more. - As soon as the flatworms start to die commence with the activated carbon to take out any toxic body fluids. Also see the above given important remarks. - After an hour or so you can turn any UV or ozone on again.