It’s easy to get a little greedy. Continuing to build and build. Now I have turned my two columns into four with the help of these instructions from @gaiatechnician (Brian White), I managed to use a pump with two outlets to provide four columns with water. I have used 6 T-connections and 4 air controls.
The pump is on a timer that is on every half hour between 09:00 and 22:00. The fluorescent lamp is running from 08:00 to 21:00. It was a bit difficult to balance the air flows, but now it seems to be fairly stable.
My system is generally quite unstable, probably because my water tank is so small (less than 1,5l) and the tubes have a tendency to float or move in the water tank.
Lettuce, paprika, pepers, tomato and basil. The paprika I got from a friend. All plants are grown from seeds.