The Hydro system has a container of water on the bottom that uses an air pump to take water up to the top of the column through tubes. The water drips from one planter down through the next two and recycles the water through the system. Depending on what I’m growing, I use liquid nutrients mixed in the water.
The plans for the original system can be found here: http://www.windowfarms.org/
- Window Farm (busyasabeazer.wordpress.com)