For optimal results, we always recommend measuring by weight. Masterblend is highly concentrated, so a difference of one or two grams will have an impact on your nutrient solution, especially in a smaller system. If you cannot get a scale, you can measure by volume by converting the Dosing Table on your label as follows:
1 tbsp (3 tsp) of Masterblend = 18g
1 tbsp (3 tsp) of Magnesium Sulfate = 15g
1 tbsp (3 tsp) of Calcium Nitrate = 19g
When mixing 25 litres of nutrient solution, 1 tablespoon of Masterblend, 1.5 teaspoons of Magnesium Sulfate and 1 tablespoon of Calcium Nitrate should get you close to the right nutrient levels.