Theoretically there are six types of hydroponic systems. Of course hydroponics systems come in too many variations for anybody to be able to index them all, but essentially any of those system variations can be defined as a combination between the primary hydroponics systems. Let's have a look at their main features and see what they consist of.
This method of growing hydroponically is very easy and is an ideal introduction to growing without soil. It also needs very little equipment, yet should still allow you to grow plants better than simply in soil. The system is set up by filling up a pot with some medium for the plant to grow in, rather than soil this could be either perlite or clay pebbles which are both popular neutral growing mediums and are easy to purchase in garden centers. The medium is rinsed thoroughly before being placed into the growing pot. If you are using perlite make sure you rinse this in a well ventilated area as dry perlite is very dusty, also make sure the pot you are using has drainage holes in the bottom. The plant is then placed into the medium like you would plant a normal plant into soil. I have grown my plants from seed and grown them entirely in rockwool cubes so I can just place the cube with the plant straight into the pot. This also means no mess, apart from the perlite which can make the area look like it's just snowed and it also gets very sticky when wet. The pot and plant is then placed into a pot saucer tall enough for quite a bit of nutrient solution(Water and Nutrients) to sit in, the nutrients are then used to water the plant as you would water a normal plant in a pot so that the nutrients flow through the medium into the saucer at the bottom. This process will probably only need to be done every few days when the plant is small but might need to be done once or maybe twice a day if it's warm weather or the plant is growing large and using lot's of nutrients
This method is the kind of hydroponics system most people think of when they think about hydroponics. N.F.T. systems have a constant flow of nutrient solution so no timer required for the submersible pump. The nutrient solution is pumped into the growing tray (usually a tube) and flows over the roots of the plants, and then drains back into the reservoir. There is usually no growing medium used other than air, which saves the expense of replacing the growing medium after every crop. Normally the plant is supported in a small plastic basket with the roots dangling into the nutrient solution. N.F.T. systems are very susceptible to power outages and pump failures. The roots dry out very rapidly when the flow of nutrient solution is interrupted.
This method is probably the most high-tech type of hydroponics gardening. Like the N.F.T. system the growing medium is primarily air. The roots hang in the air and are misted with nutrient solution. The misting 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. A timer controls the nutrient pump much like other types of hydroponic systems, except the aeroponics system needs a short cycle timer that runs the pump for a few seconds every couple of minutes.
This method isprobably the most widely used type of hydroponic system in the world. Operation is simple, a timer controls a submersed pump. The timer turns the pump on and nutrient solution is dripped onto the base of each plant by a small drip line. In a Recovery Drip System the excess nutrient solution that runs off is collected back in the reservoir for re-use. The Non-Recovery System does not collect the run off. A recovery system uses nutrient solution a bit more efficiently, as excess solution is reused, this also allows for the use of a more inexpensive timer because a recovery system doesn’t require precise control of the watering cycles. The non-recovery system needs to have a more precise timer so that watering cycles can be adjusted to insure that the plants get enough nutrient solution and the runoff is kept to a minimum. 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.
This is by far the simplest type of hydroponics system. This is a passive system, which means there are no moving parts. The nutrient solution is drawn into the growing medium from the reservoir with a wick. This system can use a variety of growing medium. Perlite, Vermiculite, Pro-Mix and Coconut Fiber are among the most popular. The biggest draw back of this system is that plants that are large or use large amounts of water may use up the nutrient solution faster than the wick(s) can supply it.
This works by temporarily flooding the grow tray with nutrient solution and then draining the solution back into the reservoir. This action is normally done with a submerged pump that is connected to a timer. When the timer turns the pump on nutrient solution is pumped into the grow tray. When the timer shuts the pump off the nutrient solution flows back into the reservoir. The Timer is set to come on several times a day, depending on the size and type of plants, temperature and humidity and the type of growing medium used. The Ebb and Flow is a versatile system that can be used with a variety of growing mediums. The entire grow tray can be filled with Grow Rocks, gravel or granular Rockwool. Many people like to use individual pots filled with growing medium, this makes it easier to move plants around or even move them in or out of the system. The main disadvantage of this type of system is that with some types of growing medium (Gravel, Growrocks, Perlite), there is a vulnerability to power outages as well as pump and timer failures. The roots can dry out quickly when the watering cycles are interrupted. This problem can be relieved somewhat by using growing media that retains more water (Rockwool, Vermiculite, coconut fiber or a good soilless mix like Pro-mix or Faffard’s)
This is the simplest of all active hydroponics systems. The platform that holds the plants is usually made of Styrofoam and floats directly on the nutrient solution. An air pump supplies air to the air stone that bubbles the nutrient solution and supplies oxygen to the roots of the plants. 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 hydroponics system. Very few plants other than lettuce will do well in this type of system. This type of hydroponics system 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 draw back of this kind of system is that it doesn’t work well with large plants or with long-term plants.