For small volumes, it can be difficult to measure 0.25ml or 0.5ml precisely. A practical method is to dilute 5ml of Ecothrive Trace in 1 litre of water to create a stock solution. To use this stock solution: For 0.25ml per litre: Mix 50ml of the stock solution with 1 litre of water. For 0.5ml per litre: Mix 100ml of the stock solution with 1 litre of water. Store the stock solution in a cool, dark place in a well-sealed container.