| How to Make an Active Hydroponic Unit
The Flood System
The flood system consists of a tub or container holding a medium that is completely flooded on a regular basis, usually once, twice, or three times daily, depending on the growth stage and environmental factors. The medium holds enough moisture between irrigations to meet the needs of the plant. First-generation commercial greenhouses using this method were usually built with long beds of gravel that were systematically flooded. Today, the flood system is most often used with individual containers, where each container is attached to the reservoir by tubing or by a leak-proof seal. The
Medium
With this system, growers have a choice of mediums, including sand, pebbles, chopped-up rubber tires, pea-sized lava, gravel, and
vermiculite-perlite-Styrofoam mixtures. A recommended mixture for this setup would be one part each of perlite and Styrofoam, and two parts vermiculite, or one part vermiculite and four parts lava. Note that because perlite and Styrofoam are lighter than water and will float if this system is fully flooded, neither should be used as a stand-alone medium with the flood system. Construction and
Maintenance
A simple flood system can be constructed using a container with a tube attached to its bottom and a one-gallon jug. Fill the container with the medium. Each day, pour the water/nutrient solution from the jug into the container, holding the tube up high enough so that no water drains out. Then let the tube down so that the water drains back into the jug. Some water will have been absorbed by the medium, so fill the jug to its original level before the next watering. The plants' water needs increase during the lighted part of the daily cycle, so the best time to water is when the light cycle begins. If the medium does not hold enough between
waterings, water more frequently. Flood systems can be automated by using an air pump to push water from the reservoir into the growing unit. The Drip Emitter
System
Drip emitters are complete systems that can be bought in nurseries or garden shops. They have been used for years to water individual plants in gardens and homes. They can also be used with a central reservoir and a pump so that the water/nutrient solution will be redistributed periodically. If you choose this system, make sure to buy self-cleaning emitters so that the dissolved nutrients do not clog them with salt deposits. Start pumping about a gallon every six hours during daylight hours. Drip emitters can be used with semiporous mediums such as ceramic beads, lava, gravel, sand, or
perlite-vermiculite-Styrofoam mixtures. The Aerated Water
System
The Aerated water system is probably the most complex of the hydroponic systems, and because it allows the least margin for error, it should be used only by growers with previous hydroponic experience. To put together an aerated water system, you must first construct a clear air channel in your container. This is done by inserting a plastic tube cut with holes through the medium. Then a fish tank aerator is placed at the bottom of the plastic tube. The air channel allows the air to circulate without disturbing the roots, and the roots use the oxygen dissolved in the water.
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