There are two categories of hydroponic systems: aggregate and non-aggregate. Non-aggregate hydroponic systems are designed to support plants with their roots hanging into the nutrient solution. Aggregate hydroponic systems use substrates to provide support for the plants. In aggregate hydroponics, the systems may be a closed or open system. An open system denotes that the system does not recycle the nutrient solution whereas a closed system does recycle the nutrient solution (non-aggregate systems are mostly closed systems).

The first non-aggregate system is the float bed (deep raft, raft, deep flow, and deep channel) system. The float bed generally uses a large piece of Styrofoam with 2 or 3 inch holes cut into it. Net pots are inserted into these holes. The net pots provide support to the plants and the Styrofoam provides the floating feature to the system in a large tub of water. An air pump outside of the tub is connected to an airstone inside the tub via plastic tubing. This setup provides the roots with air, which is necessary for growth, nutrient uptake and respiration.

The second non-aggregate hydroponic system is called nutrient film technique (NFT). NFT systems use the same concept of having the roots in nutrient solution. Instead of plant roots suspended in a large tub, NFT has the plant roots suspended in “channels” where holes are cut on the top of the channels to allow for net pots to hold the plants. These channels are sloped so that thin layers of nutrient solution can flow through. The nutrient solution is pumped to one side of the channel and flows to the bottom of the channel by gravitational force. At the bottom of the channel, the nutrient solution collects in a sump tank that is recycled back to the top of the channels by the water pump. Unlike float bed systems, NFT systems do not allow for complete root submersion i

nto the nutrient solution. The plant roots are fed nutrients only by a thin layer of nutrient solution, where the rest of the channel is empty space designed to allow for air flow to the roots.

The third non-aggregate hydroponic system is aeroponics. In this design, plants are suspended in net pots put in holes that are cut out of a plastic panel (similar to the float bed system and the NFT system). The roots are suspended below the plastic panel in and enclosed open space. The roots are periodically sprayed with a nutrient solution every 2-3 minutes for a few seconds to keep the roots moist. A misting system along with a timer controls the spraying times. The excess moisture from the spraying is eventually collected at the bottom of the enclosure to be re-sprayed on the roots.

The first aggregate hydroponic system is the drip system.

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Originally posted by Scott Moore for Stuppy Greenhouse