Basic marijuana hydroponic rockwool system

This system is based on normal commercial practice in production of marijuana. It is designed for mono-cultural cultivation and is not suitable for mixed gardening. This design is for recirculation of nutrients, if you intend to use a total loss system, you will need a larger tank and provision for run-off. Cultural practices will differ with total loss as opposed to re circulation.

This basic hydroponic Rockwool system will suit a larger growing area and is highly recommended with the following provisions.

Most plants grown in this system will need support from the above. This is especially true of climbing plants such as marijuana.

This system is based on the use of aqua trays in steel channels. Each tray is 4.3 feet | 130 cm long and contains one slab. Plant spacing will depend on the crop but will usually be between two and six marijuana plants per slab.

Steel channel is recommended to hold the aqua trays. This can be acquired at any sheet metal workshop where it will be folded to your requirements. The lightest gauge will do and it must be galvanized. Remember to line the channel with plastic sheet to ensure that nutrient solution does not come into contact with the metal. An extra length of the same channel will serve to collect the nutrient run-off at the end of the channels and return it to the tank.


The tank position is dictated by the system layout. It must be below the lower ends of the rows and also needs to be close to the tap or hose end. Tank volume should be at least two liters per marijuana plant in the system. Larger volume is better. Flow rate at all drippers should be approximately the same. This is easily measured with a jug and a stopwatch. In larger systems, there may be a fall off in pressure between the rows with the furthest row getting inadequate supply. If this happens, an extra PVC pipe should be added to join points A and B. This will equalize pressure in the system and ensure that all drippers run equally. In most set ups this will be unnecessary and point B can be closed off with an end cap.

A line filter should be included between the pump and the outlets to guard against dripper blockage. This filter will require regular checking.

A bypass should be included in the tank | pump set up. This will serve two purposes, firstly it will provide accurate control of supply to the drippers. This will be achieved by adjustment of the gate valve on the bypass. Secondly, it will ensure that the pump runs freely and adds high levels of oxygen to the nutrient solution.

Although this is a very simple system, there are certain things to bear in mind before embarking on it. In the first place the tank should be as large as practically possible. This is because the conductivity and pH of the solution will be changing all the time and a large tank will minimize the effects of this and reduce the number of times that you will need to check the solution. For commercial marijuana growers it is advisable to retain at least two liters of tank volume per cannabis plant in the system. The larger the tank, the better. It is also very important to ensure that the nutrient is sufficiently oxygenated. Fortunately this is very easy to achieve because there will be excess pumping capacity that can easily be diverted back to the tank.