A lettuce raft is probably one of the most simple of hydroponic systems to build. Since rafts are only suitable for light-weight, low-growing plants, they are ideal for lettuce gardening.
Cut Holes in the Styrofoam
With a sharp knife cut holes in the Styrofoam to support the net cups.
Connect the Pump
Connect the pump to the diffusion stone with a length of aquarium quality plastic tubing.
Decide Where to Locate the Raft
The raft should be located near a free power point to supply the power for the pump. It should also be in natural light as much as possible.
Pour nutrient solution into the container until it is about 6 inches deep. Place the diffusion stone in the solution and switch the pump on immediately. This will aerate the solution and you will be able to confirm that enough bubbles are being produced.
Float the Raft
Place the Styrofoam raft on top of the solution so that it is floating.
Insert the Plants
Put each of the plants in the net cups into the holes in the Styrofoam raft. Once they are evenly distributed the raft will lose the tendency to flip over.
Secure the Styrofoam
It can sometimes be a good idea to put weights at the four corners of the Styrofoam raft so that it will settle a little deeper and be more stable.
The bubbles from the diffuser will rise straight up but the aerating effect on the nutrient solution is enough to ensure that the roots of all the plants will find oxygen easy to absorb.
Do not switch off the air pump and leave the diffuser in the nutrient solution. Take the opportunity to soak the diffuser in fresh water and dissolve out any salts that might have accumulated. Without attention the diffuser can become blocked, so you will need to check it regularly.
Floating rafts over nutrients ensures that the plants get plenty of nutrients and the diffuser makes sure that they also get enough oxygen.