Understanding the 7 Most Common Hydroponic Systems

Hydroponic gardening may seem intimidating to novice gardeners or home hobbyists. However, what many gardeners don’t realize is that hydroponic gardening is not as complicated as they may think. In fact, hydroponic gardening is simply growing plants without soil. Now, I know that fact in itself may be intimidating, especially for gardeners who have taken many years to master the science of soil but growing plants hydroponically works on many of the same principles as growing plants in soil.

Growing Without Soil

The main difference between soil and hydroponic gardening is that hydroponic gardens do not use soil. Even though this is a very big difference, all the other factors that attribute to healthy plant growth remain the same. A plant’s lighting needs and environmental factors, such as temperature and humidity, will still need to be addressed whether the plants are grown in soil or a hydroponic system. In order to fully grasp the concept of hydroponic gardening, all a gardener really needs to do is understand the difference between growing in soil and growing without soil. In a traditional soil garden, the microorganisms within the soil help break down organic matter into nutrients that can be easily absorbed by the plants. In a hydroponic system, most of the synergistic relationships between a plant and the microbes (normally found in the soil) are bypassed. Prior to being packaged, fertilizers specifically designed for hydroponics are broken down into a form which can be absorbed by the plants. In other words, the nutrients found in hydroponic fertilizers have been broken down in a laboratory and bypass the need for microorganisms to break them down. Hydroponic fertilizers are usually water soluble because they need to be stable in a reservoir and also be able to be circulated through a hydroponic system. There are many different hydroponic systems available. A closer look at some of the most popular hydroponic systems will give a hobbyist a good idea of which system may be a good one to start experimenting with.

NFT hydroponic systems are frequently used for growing lettuce and other greens.
Nutrient Film Technique

Nutrient film technique, or NFT, is one of the most commonly used systems in commercial greenhouses for growing lettuce and other greens. NFT is a system that supplies a plant’s roots with a continuous flow of nutrient solution through a series of tubes or gutters. The “film” is referring to the thin layer of nutrient solution that covers the bottom of each tube or gutter. To make a “film” of nutrient solution, these systems use a low volume pump to create a continuous trickle. The tubes or gutters are positioned at slight angles, allowing gravity to return the nutrient solution to the reservoir or the subsequent tube or gutter. NFT systems are great for hobbyists because they are simple to build and maintain. In fact, most of the components needed to build a NFT system can be found at any home supply store. When considering using a NFT system, a gardener must think about the size of the plants to be grown. Finishing large plants in NFT systems can be difficult because large plants have large root masses. Oversized roots in a NFT system can be cumbersome and may clog tubes or plug gutters. Some growers will trim the roots in a NFT system but I usually do not recommend this as it could cause stress to the plant and hinder growth.

Top Feed

A top feed, or top drip, hydroponic system is a system where a feed line is directly attached to the base of each plant. A pump, normally controlled by a timer, intermittently supplies each plant with nutrient solution. Some top feed systems continually supply nutrient solution to the plant with a slow drip; however, these should generally be avoided by novice gardeners because there is a good chance of over or under watering with this particular set up. Top feed systems can be set up as either a run to waste system (the nutrient solution goes down the drain after feeding the plants) or a recirculating system (the nutrient solution is collected in a reservoir after feeding the plants to be reused for feeding again later). Top feed systems are very popular for commercial growers, especially those using rockwool as the medium. Many of the commercial hydroponic tomato growers use top feed systems. In order to maximize efficiency, it is best to have inline valves at each plant site which allow the flow rate to be controlled for each individual plant. A plant’s size, genetic make-up and position in the greenhouse can affect its water uptake and the ability to adjust the flow of nutrient solution is crucial for optimizing growth. Top feed systems are fairly easy to set up, although a hobbyist with a large space may first want to experiment with a small system before converting the entire garden to a top feed hydroponic system.

Flood and Drain

Flood and drain, also known as ebb and flow, hydroponic systems are another popular choice among both commercial and hobbyist gardeners. A flood and drain system utilizes a table or trough that is flooded with nutrient solution for a given period of time and then drained. To avoid the need for a second pump, traditional flood and drain systems use gravity to return the nutrient solution to the reservoir. The plants within the table can be planted into a medium such as hydroton, stone wool, coco coir, or another soilless mix. The medium can be placed directly into the table or individual containers can be used so that the plants can be transferred to another table as they mature. Some growers may have three or four tables set up, each for a different stage of growth. As the plants grow, they can be moved to the appropriate table. This is convenient because the lighting, nutrition, and atmospheric conditions can be customized for each stage of growth. Flood and drain systems work well for beginner gardeners looking to experiment with hydroponics because they are easy to build and can accept a range of media. Flood and drain systems can also offer a hybrid soil/hydroponic system to growers who are not ready to give up soil gardening completely but still want to gain some of the benefits hydroponic gardening has to offer.

Deep Water Culture

Deep water culture, or DWC, is a system in which the plant’s root mass is mostly submerged in water and additional oxygen is delivered via an air pump. When water temperatures are kept between 65-70 degrees F, this system has particularly fast growth, which is unmatched by almost any other hydroponic system. Due to its speed, this system has been a favorite of growers who want to grow big plants as fast as possible. Many home hobbyists experiment with DWC because an individual module can be made from a five gallon bucket and a small aquarium pump. The downfall for most beginners who experiment with DWC is fluctuating water temperatures. Water temperature fluctuation is unforgivable especially when temperatures exceed 75 degrees F. As water gets warmer, it loses its ability to hold dissolved oxygen. This, in turn, leaves a plant’s root mass susceptible to anaerobic pathogens. The best way to combat this is to prevent the water from ever getting too warm. Although most hobbyists who are just experimenting with hydroponics will not want to invest in a water chiller, any serious DWC cultivator will find a water chiller to be an essential tool for maintaining consistent results with a DWC system.

Undercurrent Systems

Undercurrent systems are similar to Deep Water Culture systems in that the roots are mostly submerged in water and the oxygen is supplied by an air pump. In an undercurrent system, a submersible pump continuously moves the nutrient solution between plant modules creating an undercurrent, hence the name. One huge advantage of undercurrent systems is the uniformity of the nutrient concentration and the pH in the solution. This makes monitoring nutrient and pH levels a breeze and adjustments to the solution much easier for the gardener. The constantly circulating water allows undercurrent systems to withstand slightly higher temperatures than a DWC system. One consideration for undercurrent systems is the water flow from module to module. Just be sure when purchasing or designing an undercurrent system that the connections between modules are large enough that roots (especially of larger plants) will not hinder the flow of the nutrient solution.

Aeroponics and Fog Systems

Aeroponic and fog systems are hydroponic systems that sporadically spray or mist a plant’s root mass with nutrient solution. Aeroponic systems generally utilize spray nozzles to create small droplets of nutrient solution. Some aeroponic systems create a “dry fog” by reducing the droplet size to as small as 5 microns, hence the term “fog system”. It is absolutely imperative to use a fully soluble nutrient solution with these systems. Nutrient solutions that are not fully soluble will leave residue and eventually clog the misters or spray heads. Just about any type of plant can be grown in an aeroponic or fog system. Aeroponic or fog systems are not as susceptible to warm temperatures because the root mass is not submerged in water. There is, however, more maintenance involved with an aeroponic system. Checking and cleaning spray heads or misters must be done on a regular basis. Due to the increased maintenance, aeroponic systems are usually avoided by novice growers.


Aquaponics is a hybrid of aquaculture and hydroponics. Basically, aquaponics is a system that uses the symbiotic relationship between plants and fish waste. The water in the fish holding tank and the waste produced by the fish are pumped into the hydroponic system and fed to the plants. As the plants use the nutrients in the fish waste, they act as a filter, cleaning the water. The water is then returned to the fish holding tank. For some crops, the horticulturist may need to supplement additional nutrients to supply the plants with everything they need. For example, fish waste alone may not be enough to supply a fruiting tomato plant with the proper nutrient ratios for fruit development and may need to be supplemented. More and more hobbyists are experimenting with aquaponics. Aquaponics can be done with any of the previously mentioned hydroponic systems with the exception of aeroponics. Although some gardeners have successfully combined aquaculture with aeroponics, it is difficult and requires specialty filtration and a lot of maintenance.

Hydroponic gardening is just one more way a hobbyist can expand his or her gardening hobby. Just think of the looks on your friends’ faces when they come over to see your greenhouse and you show them your hydroponic system. Hydroponics is not just for showing off to your friends (although that is one of the biggest perks.) The delivery of ready-to-use nutrients combined with highly oxygenated water creates an environment where plants experience increased growth rates. It doesn’t matter whether a gardener is after increased growth rates for their plants or for the bragging rights on the block because hydroponic gardening will provide both.

Eric Hopper is a MyGardenAndGreenhouse.com contributing editor.

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