There are six basic types of reservoir-based hydroponic systems; Wick, Deep Water Culture, Ebb and Flow (flood and drain), Drip (recovery or non-recovery), N.F.T. (Nutrient Film Technique) and Aeroponic. There are hundreds of variations on these basic types of systems, but all hydroponic methods are a variation (or combination) of these six.
The passive wick system is by far the simplest type of reservoir-based hydroponic system. A nutrient solution is drawn into the growing medium from a reservoir with a wick acting like a sponge and absorbing the solution from below.
Most wick systems use a variety of popular growing medium such as perlite, vermiculite, Pro-Mix and coconut fiber.
The biggest drawback of this system is that large plants use large amounts of water and may use up the nutrient solution faster than it can be supplied.
Deep water culture
The deep water culture system is the simplest of all active hydroponic systems. A platform, usually made of Styrofoam, holds the plants and floats directly on a nutrient solution in a reservoir. Oxygen supplied to the roots by an air pump and air stone; bubbles the nutrient solution.
The deep water culture is the system of choice for growing leaf lettuce, which are fast growing water loving plants, making them an ideal choice for this type of hydroponic system. Very few plants other than lettuce do well in this type of system.
Deep water culture is great for the classroom and is popular with teachers. A very inexpensive system can be made out of an old aquarium or other water tight container.
The biggest drawback of this kind of system is that it doesn't work well with large plants or with long-term plants.
Ebb and flow - (flood and drain)
An ebb and flow system works by flooding a grow tray temporarily with nutrient solution and then allowing the solution to drain back into the reservoir. The flooding action is done with a reservoir containing a submerged pump that is connected to a timer.
The timer comes on several times a day, depending on the size and type of plants, temperature and humidity and the type of growing medium used.
The versatile ebb & flow system uses a variety of growing mediums such as Hydroton Grow Rocks, coconut fiber, a good soilless mix like Pro-mix or different types of Rockwool. Many people use individual pots filled with growing medium for portability to move plants around or even in or out of the system.
The main disadvantage of the ebb & flow system is that power outages as well as pump and timer failures can cause the roots to dry out when the watering cycles are interrupted.
Drip Systems -
(recovery / non-recovery)
Drip systems are a very popular type of hydroponic system. Operation is simple; a timer controls a submersed pump that drips nutrient onto the base of each plant by a small drip line. In a recovery drip system the excess nutrient solution runoff is collected back in the reservoir for reuse. The non-recovery system does not collect the runoff.
A recovery system is more efficient since nutrient solution is reused and also allows for the use of an inexpensive, simple timer because precise control of the watering cycles is not required. The non-recovery system needs a more precise timer for watering cycles to ensure adequate nutrient solution and minimum runoff.
The non-recovery system requires less maintenance due to the fact that the excess nutrient solution isn't recycled back into the reservoir, so the nutrient strength and pH of the reservoir will not vary. This means that you can fill the reservoir with pH adjusted nutrient solution and then forget it until you need to mix more. A recovery system can have large shifts in the pH and nutrient strength levels that require periodic checking and adjusting.
N.F.T. (Nutrient Film Technique)
N.F.T. is the type of hydroponic system most people think of when they think about hydroponics. N.F.T. systems have a constant flow of nutrient solution so no timer is required for the submersible pump. The nutrient solution is pumped into the sloped growing tray (usually a tube) and flows over the roots of the plants, and then drains back into the reservoir.
No growing medium is used other than air, which saves the expense of replacing the growing medium after every crop. The plant is supported in a small net pot with the roots dangling into the nutrient solution.
N.F.T. systems are susceptible to power outages and pump failures. The roots dry out very rapidly when the flow of nutrient solution is interrupted.
The aeroponic system is the most high-tech type of hydroponic gardening. Like the N.F.T. system the growing medium is primarily air. The roots hang in the air and are misted with a nutrient solution. The mistings are usually done every few minutes. Because the roots are exposed to the air like the N.F.T. system, the roots will dry out rapidly if the misting cycles are interrupted by power outages and pump failures.
A timer controls the nutrient pump much like other types of hydroponic systems, except the aeroponic system needs a more complex short cycle timer that runs the pump for a few seconds every couple of minutes to keep the roots wet.
Stop by your local hydroponic center to see which system is right for you.
Don and Sandy Landers are owners of Dream Garden Hydroponics, LLC, 26380 State Route 7, Marietta.