Hey arche,

Take a look at the video under the lettuce section on this forum to see how this system works. They are using rafting with constant flow which means there is no grow media. The grow tables are actual tanks about 12 inches deep and the water level is controlled by being continuously being pumped in and flowing out through the preset overflows maintaining the desired depth.

The rafts are Styrofoam and reusable if handled carefully. I don’t know about where you live, but here in the US you can buy 4’ X 8’ sheets of Styrofoam at building supply stores at a very reasonable price.

With planning and forethought, your can grow almost any veggie you want using this system. Tomatoes for example can be grown this way by running stringer bars in the overhead of the greenhouse and then tying the tomato vines up to the stringers with string taking the weight of the plants and fruits off the floating Styrofoam. The same with cucumbers, beans, peas, okra and on and on. This is the system Codi and I used and it worked like a charm.

We built our grow tables using treated plywood, 2” by 4” and 4” by 4” and covered the table interior with 6mil black plastic. As for the bio-filter we also went to the building supply store and purchased the largest AC filters we could find, the kind you cut to size that has no frame that are about an inch or so thick.

Might sound like a lot of work but we used small nylon line and hand sewed them together until we had a section some 10’ across and 4’ high. We laced this to a section of 1 ½“ PVC pipe capped on one end.

We had drilled small holes in the bottom side of this pipe which faced the filter material. We then laced the PVC pipe to a reinforced stringer bar at the back end of the Green house suspending it in the air and attached it via more PVC to our water pump which was submerged in our sump tank (a blue rubber (plastic) 55 galleon barrel which was partially buried in the ground between the fish tanks. Reason for the sump tank being buried was it had to be below the overflow level of the fish tanks because it was gravity fed from the fish tanks.

The bio-filter was suspended over a 12’ section of 12” PVC capped at both ends which was suspended between two 4” X 4” post. The bottom side was at an elevation higher than the grow tables. We drilled 3” holes in the bottom of it about 12” apart and put in 3” connectors and attached PVC pipes which ran to the flow beds.

The water was pumped from the sump tank to the bio-filter, gravity fed to the flow beds which in turn was gravity fed back to the fish tanks which had overflow pipes to gravity feed the sump tank. Wa-La ….. worked like a charm.

We also mounted fans behind the bio-filter material and turned them on during the summer to add moisture to the air and cool the greenhouse.

I hope this helps if for nothing else if you don’t like the system, maybe some ideas of your own.