When choosing a hydroponic system it's important to keep in mind the size of the plants you intend to grow. Large plants will need more room between them to grow properly. So for plants larger than two feet tall, it's usually better to grow with individual containers that can be moved around. Plants smaller that two feet can be grown in small pots placed in a tray so you can water all of them at once.
The WaterFarm and PowerGrower from General Hydroponics are good if you are growing a few large plants. They are self contained drip systems. The solution is stored in the bottom and pumped up with an air pump.
The Multi Flow is a flood and drain system designed for growing many large plants. The nutrient is stored in the reservoir and pumped through the controller to the pots by a pump. A second pump drains the solution out after a short time.
The RainForest is an aeroponic system used for small plants or cuttings. The nutrient solution is stored in the bottom and is drawn up with a vaporizing spinner that sprays the dangling roots. This type of system gives the plants a very large and healthy root system.
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