Media-Based
The best feature of media-based systems is their ability to hold nutrients and moisture between watering cycles so plants can survive a temporary breakdown or power outage. But with that security comes the cost and mess associated with the growing media. Some gravel media can even leach mineral substances into the solution, resulting in chemical imbalances. Nevertheless, media-based systems remain popular--especially among beginners--because of their relative simplicity and reliability.
Ebb-and-flow systems function by flooding and draining a medium-filled growing bed with nutrient solution. In its basic form, the ebb-and-flow unit consists of a growing tray and reservoir bucket connected by a tube. The tray is flooded by manually raising the bucket and drained by lowering it. By adding a pump and timer, the basic unit evolves into an automatic hydroponic system.
Top-feed or drip systems work with a timer-controlled pump that delivers nutrient solution slowly and regularly to the base of the plant roots through thin tubing or drip emitters. The solution trickles through the medium back to the reservoir below the growing bucket. Media such as expanded clay pellets or perlite distribute the nutrient in a wide circle around the plant roots.
Drip systems are flexible. You can adjust the nutrient flow for individual plants within the same system by changing the number of emitters or their size, allowing plants with different nutrient and water requirements to be grown together.
Although drip systems are easy to set up, construct, and operate, maintenance can be a problem, especially if you use organics in your nutrient solution. The emitters clog on occasion and then need thorough cleaning.
See the self-watering potted plant in the Easy Hydroponic System Plans section for a basic example of a media-based grower.