I started a garden project for my small space, to have a vegetable garden on my condo balcony. The garden is a “grow bag” garden based on Larry Hall’s Kiddie Pool Grow Bag Garden System. The idea is that porous grow bags are filled with potting mix and sit in 2″ of water in a basin. The original design uses reusable Walmart shopping bags in a kiddie pool with 2″ of water. There’s a hole cut out at 2″ up the side of the basin to allow overfill water to drain out in case it rains. To keep mosquitoes from breeding in the water, you can fill the basin up 3″ deep with pea-sized pebbles. The water only comes up 2″ so the water is below the top of the pea gravel.
My take on the design was to build a rectangular basin to hold 2 rows of grow bags, and to put it on my condo balcony, maximizing my usable space. I would line the basin with a thick plastic pond liner to hold the water. I also wanted a stand for a rain barrel which would supply water to the basin. There would be a float valve (like you have in your toilet tank) in the basin to regulate the flow of water into the basin automatically. If the water level falls below 2″, the float valve would allow water to flow into the basin then shut-off when the water level reaches 2″.