The major benefit of a bubbling hydroponic system is that the nutrient solution carries more dissolved oxygen. The plants can divert more energy into growth because of the ready availability of oxygen.
Any hydroponic system that operates with a reservoir can be easily converted to a bubbling system. All that is required is to lower a diffusion stone connected to a quiet aquarium air pump into the reservoir. When the pump is activated air will bubble through the nutrient solution. The millions of tiny air bubbles present a relatively large surface area to the liquid and help create an oxygen-infused nutrient.
Some plants are able to survive even if their roots are totally immersed in water as long as there is sufficient available dissolved oxygen. To build a raft system is very simple.
Cut Holes in the Styrofoam
With a sharp knife cut holes in the Styrofoam slightly smaller in diameter than the tops of the net cups.
The Diffusion Stone
Connect the diffusion stone to the pump with a length of aquarium quality plastic tubing.
Locate the Raft System
The raft system requires an available power point for the pump and good natural daylight for as many hours in the day as possible.
Mix the nutrient solution and check that the Ph level is between 6 and 6.5. Fill the container to about a 6-inch depth. The diffusion stone should be placed in the solution and switched on immediately. Check to ensure that there is a good rate of bubbling to ensure effective oxygenation.
Float the Raft
Place the Styrofoam on top of the solution. It should be floating on the surface of the solution.
Introduce the Plants
Each of the net cups will be placed in one of the holes you cut into the Styrofoam. There will be a tendency for the Styrofoam to flip over so keep control over it.
Weight the Styrofoam
A weight attached under each corner of the Styrofoam can help to make it more stable. The weights will help to lower the center of gravity of the Styrofoam and plants.
Although the bubbles from the diffuser will rise straight up the aerating effect on the solution is not diminished. The bubbling will create a small turbulence in the water so that all of the solution will be exposed to the bubbles over a period.
The diffuser is in a concentrated solution of various salts and they can start to block some of the airways. Once a week switch off the pump and place the diffuser into a container of fresh water. Let it soak for a while with the pump running and you should see the quantity of bubbles increase as the salts dissolve out.
Raft systems are very low maintenance. The plant roots have little danger of drying out since they will be under the surface of the nutrient solution.