Plants require a certain set of nutrients to grow properly. In most cases, these nutrients are provided by the soil the plants are growing in. In hydroponic gardening, these nutrients are provided by a nutrient solution that includes macronutrients, which plants need in large amounts, such as carbon, nitrogen, phosphorous and magnesium; and micronutrients such as iron, copper and zinc, which plants need in smaller amounts.
Multiply the number of plants you are growing by how many days of nutrient solution you wish to make to find how many plant days you are making solution for. Divide the number of plant days by 200 liters to discover how much nutrient solution each plant needs per day.
Buy two concentrated nutrient solutions from your local garden center or online supplier, one containing the macro and the other the micro nutrients. These are sold separately to prevent devaluation of the chemicals' effectiveness.
Measure out the proper amount of chemicals from each concentrate bottle. Most nutrient solutions require you mix 100ml of solution to 10 liters of water. Divide the solution according to your plants' daily needs to avoid making too much.
Fill the soda bottles with your deionized water and nutrient solution using the funnel, and shake the solution thoroughly.