@Simon_C We bought this one; there are plans for variations on line. There is no dirt purely hydroponic, a timer controls the water flow I use 15 minutes on 15 off around the clock. For cooler weather planting 15 on and 30 off works well. There is also a timer for the grow lights that are needed when indoors. Each section has holes that direct the water from below over the roots below and back to the reservoir below. Plants seem to grow larger and faster using this method. Once it was first ready I could harvest daily throughout the winter. The small leaf lettuce got tired after a few months and I replanted it.