Types of Hydroponic Systems

Hydroponics involves growing plants in a nutrient solution rather than in soil. Growing mediums like rockwool, LECA, perlite, or coco coir provide mechanical support for the plant.

There are a number of benefits to growing plants hydroponically. One benefit is that plants often grow more quickly in hydroponic systems because the grower is providing the ideal balance of lighting, nutrients, and water. Another benefit is it conserves water. Finally, hydroponics tends to attract fewer pests than conventional soil gardening.

There are several types of hydroponic systems used by growers. These systems share many similarities, but there are also important differences between each system.

Hydroponic growing systems can be classified as either active or passive. Passive hydroponics does not involve pumps or moving parts. Instead, passive hydroponic systems rely on capillary action through the growing medium. In contrast, active hydroponics requires the use of pumps and air stones to move the nutrient solution to plant roots.

Here is a table that summarizes the main types of hydroponic systems.

Method	Passive or Active	Complexity	Description of Method
Kratky Method	Passive	Simple – suitable for beginners	Plants are placed in a growing medium that wicks water from a reservoir full of nutrient solution.
Ebb and Flow	Active	Intermediate	A growing tray containing plants is regularly flooded with a nutrient solution. It is also called flood and drain hydroponics.
Nutrient Film Technique (NFT)	Active	Intermediate to Advanced	Plants are placed in a sloping channel (typically a PVC pipe) that has a constant flow of nutrient solution.
Deep Water Culture (DWC)	Active	Simple (Simplest Active Hydroponics Technique)	The roots of the plants are suspended in a reservoir full of nutrient solution. This reservoir is constantly oxygenated by pumps and air stones.
Drip Hydroponics	Active	Intermediate to Advanced	This method is very similar to the drip irrigation systems used in conventional soil gardening.
Aeroponics	Active	Advanced	The roots of the plants are sprayed with mist regularly. This method is also called fogponics.

I will discuss each of these methods in further detail below.

Kratky Method

The Kratky method is a passive hydroponic growing technique that involves placing plants in a growing medium that wicks water from a reservoir full of nutrient solution. Eventually, the roots of the plant grow down to the water surface. This method is named for Dr. Bernard Kratky, a professor at the University of Hawaii at Mānoa.

Kratky hydroponics is probably the easiest way for beginners to get started in hydroponics. Because there are no moving parts (e.g., pumps, air stones, or water lines), it is fairly easy to set up.

A common beginner project is planting basil in mason jars. If you are not a fan of basil, this method works well with mint too. You can plant seeds in the rockwool or propagate a stem cut from a mature plant.

Note that the light entering clear glass promotes algae growth, so it is a good idea to block out the light by painting your mason jars. I use amber mason jars, and that has worked well for me so far.

Semi-Hydroponics

Semi-hydroponics, also known as semi-hydro or passive hydroponics, is becoming an increasingly popular way to grow houseplants. If you have seen people growing plants in what looks like Cocoa Puffs on Instagram, that is semi-hydro!

Semi-hydro involves growing plants in an inert growing medium. Because the growing medium does not supply the plant with nutrients like conventional soil gardening, a nutrient solution is added to the pot. The nutrient solution consists of fertilizer dissolved in water.

The “Cocoa Puffs” are porous clay pebbles that wick up the nutrient solution. This allows plant roots to obtain the water and nutrients they need to survive. Most semi-hydro systems use lightweight expanded clay aggregates (LECA) as a growing medium.

Semi-hydro works well for people who travel frequently or have little time to dedicate to taking care of their plants. Click here to read my article about growing orchids hydroponically.

Ebb and Flow

Ebb and flow, also known as flood and drain, hydroponics involves regularly flooding your growing tray with a nutrient solution. A timer is used to turn the flow on and off in an ebb and flow system.

Flooding the roots of your plants is effective because it flushes out stale, oxygen-depleted air. It also removes any excess salts that have built up on the roots.

The frequency of flooding depends on how well your growing medium absorbs water, the size of your reservoir, the type of plants you are growing.

Ebb and flow is a good system for growing heavy fruiting annuals such as tomatoes, cucumbers, and zucchini.

Components of Ebb and Flow

• Reservoir – Your reservoir can be a storage bin purchased from a big box store like Wal-Mart. Just make sure that your reservoir is opaque. A transparent reservoir can promote algae growth. It may also be a good idea to add a back-up reservoir in case your system overflows. This may be particularly important if you are setting up this type of system on nice floors.
• Growing Tray – Your growing tray could consist of a platform with holes for the net pots. Alternatively, you could place larger pots with multiple drainage holes into a shallow tub.
• Irrigation Tubing for Flooding and Draining
• Net Pots and Growing Medium – For ebb and flow hydroponic systems, LECA works well because the larger aggregates will not clog the pumps. In addition, it provides good stability to the plants.
• Water Pump
• Timer – A timer is used to turn pumps on and off.
• Nutrients – Like all hydroponic systems, you will need nutrients/fertilizers to feed the plants.
• Water – Another crucial part of every hydroponic system. Make sure you are using distilled water or high-quality tap water.
• pH Testing Kit and Thermometer – It is important to maintain a water temperature and pH that allows the plants to uptake nutrients in an efficient manner.
• Lighting – If you are going to be setting up your hydroponic system indoors, it is important to have lighting that is appropriate for the plants you are growing.

Nutrient Film Technique (NFT)

Nutrient Film Technique (NFT) is a type of hydroponics that involves a sloping channel that contains a constant flow of nutrient solution. Plants sit on top of the channel, and the roots are suspended into the flowing nutrient solution. A pump delivers water from a separate reservoir to the sloped growing channel. Unlike Ebb and Flow, water is constantly flowing through the growing tray in NFT.

It is great for growing for basil, lettuce, and other herbs. Many growers have also been successful at growing strawberries in NFT systems. Heavier crops such as tomatoes are not good crops to grow in NFT.

NFT is a popular technique for commercial growers, but it is not widely used among hobby growers.

Components of NFT

• Grow Tray/Channel – Typically, the grow tray/channel is a PVC pipe. Holes are drilled into the PVC pipe for the net pots.
• Reservoir – The reservoir contains the water and nutrients circulated in the grow tray. A 5-gallon bucket would work well as a reservoir for NFT.
• Submersible Water Pump and Associated Tubing
• Air Stones and Diffusers – The air stones will be hooked up to the air pump in order to oxygenate the water. Air stones are also used in aquariums.
• Net Pots – The net pots are used to keep plants in place so the roots can remain suspended in the nutrient solution. A growing medium may be used to keep the plants in place within the net pot, but it is optional.
• Nutrients – Like all hydroponic systems, you will need nutrients/fertilizers to feed the plants.
• Water – Another crucial part of every hydroponic system. Make sure you are using distilled water or high-quality tap water.
• pH Testing Kit and Thermometer – It is important to maintain a water temperature and pH that allows the plants to uptake nutrients in an efficient manner.
• Lighting – If you are going to be setting up your hydroponic system indoors, it is important to have lighting that is appropriate for the plants you are growing. For example, lettuce reacts best to red and blue light while tomatoes do best with full-spectrum lights.

NFT is a bit more complex to set up than other types of hydroponic systems, so it is not suitable for beginners.

Deep Water Culture (DWC)

In a Deep Water Culture (DWC) system, roots are suspended in a reservoir full of nutrient solution. DWC is also sometimes called raft systems because a platform with holes for pots containing plants is placed on top of the reservoir. DWC is the simplest active hydroponic system.

Air pumps and air stones are important components of DWC because they ensure that the roots stay oxygenated. This oxygenation is important because like the Kratky method, the roots are submerged all the time in DWC. Without oxygen, the plants will essentially drown. Oxygen is also important for maximizing the amount of nutrient uptake.

DWC is popular for a number of reasons. One reason is that it is fairly low maintenance once you set it up. There are only a few moving parts (air pump and air stones).

Secondly, there are several crops that grow well in DWC. Lightweight plants such as lettuce, kale, basil, okra, collard greens, bok choy, and chard grow well in DWC. Top-weight crops such as tomatoes are not well-suited for DWC hydroponics.

Components of DWC Hydroponics

You will need the following equipment to set up your own DWC system:

• Reservoir – Your reservoir could be an airtight bucket or an aquarium. Make sure your reservoir is large enough to accommodate the number of plants you want to grow.
• Floating Platform – As mentioned before, you will need a platform to keep your plant roots suspended in water. This could be a piece of styrofoam that is cut to fit your reservoir.
• Net Pots – Net cups will hold the plants and will be placed in the holes cut into your floating platform.
• Growing Medium – You will also need a growing medium such as Rockwool or LECA to hold the plants in place.
• Air Pump and Associated Tubing – An aquarium pump could work well depending on the size of your system. It is important to note that an air pump and water pump are not the same. Make sure you purchase a reliable air pump that can run 24/7. Unfortunately, if your pump starts working, the plants growing in your DWC system will die fairly quickly.
• Air Stones and Diffusers – The air stones will be hooked up to the air pump in order to oxygenate the water. Air stones are also used in aquariums.
• Nutrients – Like all hydroponic systems, you will need nutrients/fertilizers to feed the plants.
• Water – Another crucial part of every hydroponic system. Make sure you are using distilled water or high-quality tap water for DWC.
• pH Testing Kit and Thermometer – It is important to maintain a water temperature and pH that allows the plants to uptake nutrients in an efficient manner. In smaller DWC systems, the pH and temperature can fluctuate significantly, so it is important to test the water in your reservoir regularly.
• Lighting – If you are going to be setting up your hydroponic system indoors, it is important to have lighting that is appropriate for the plants you are growing. For example, lettuce reacts best to red and blue light while tomatoes do best with full-spectrum lights.

Drip Hydroponics

Drip hydroponics is very similar to the drip irrigation systems used in conventional soil gardening. It is probably one of the most widely used hydroponic systems (commercial and hobbyists). They are suitable for both large and small systems.

This type of system involves pumping nutrient solution from a reservoir through tubing to the top of growing media. Then excess water drains away. This water is typically recirculated in home-built systems.

The pH of recirculated water should be monitored regularly. This is because the water chemistry will change as the plants take up water and nutrients.

Dutch Bucket

Dutch buckets are a type of drip hydroponics. This type of system is typically compromised of several buckets lined up in a row. Some people use square containers called Bato buckets. A pump conveys nutrient solution from a reservoir to a water line that runs along the length of the buckets. The nutrient solution is delivered to each plant via a drip emitter.

Dutch buckets are great for growing larger plants such as tomatoes, peppers, squash. cucumbers, and eggplant.

Components of a Dutch Bucket System

• Buckets – 3-gallon or 5-gallon buckets or bato buckets.
• Growing Medium – Perlite or LECA are good growing mediums for Dutch Bucket systems.
• Submersible Pump
• Reservoir
• Drip emitters – Typically, these systems have 1 or 2 drip emitters per bucket.
• Piping and Associated Fittings/Elbows – You will need piping for the irrigation lines that convey water to the plants and piping for the recirculating water.
• Siphon Elbows for the return line
• Nutrients – Like all hydroponic systems, you will need nutrients/fertilizers to feed the plants.
• Water – Another crucial part of every hydroponic system. Make sure you are using distilled water or high-quality tap water.
• pH Testing Kit and Thermometer – It is important to maintain a water temperature and pH that allows the plants to uptake nutrients in an efficient manner.
• Lighting – If you are going to be setting up your hydroponic system indoors, it is important to have lighting that is appropriate for the plants you are growing.

Aeroponics

Unlike other types of hydroponic systems, aeroponics involves spraying or misting the roots at regular intervals. The roots are never submerged in water when they grow in an aeroponics system.

Some aeroponic systems are horizontal in nature. The foliage of the plants sits on top of a platform, and the mist is sprayed on the roots below the surface.

Towers are becoming increasingly popular in aeroponics. The vertical approach saves space.

Aeroponics can be classified as high pressure or low pressure. High-pressure systems produce droplets smaller than 50 microns. In general, plants will grow faster in a high-pressure system. However, the equipment required for high-pressure aeroponics is quite expensive, and low-pressure systems work well for hobbyists.

Aeroponics systems are complex systems and are not suitable for beginners.