3 Types of Aquaponics Systems Compared

Aquaponics is an integrated food production system that combines aquaculture and hydroponics. It has gained a lot of popularity due to its efficiency and sustainability. Aquaponics comprises three major systems, and each one has its pros and cons. 

Here are the three major Aquaponics systems:

1. Media-Based Grow Bed
2. Nutrient Film Technique (NFT) 
3. Deep Water Culture (DWC) or Floating Rafts 

We’ll take a detailed look at each aquaponics system through the rest of the article. Let’s dig in to learn each system’s features, advantages, and disadvantages. 

Aquaponics Systems Overview

There are a few things to note before discussing these aquaponics systems. All three of them have unique components and designs. However, a typical aquaponics system comprises the following: 

• Fish tank. Here is where the fish will be bred and housed. 
• Growing bed/floating rafts and media. This is the surface where your plants will grow. 
• Mechanical filters. These are screens that sieve out solid wastes. 
• Biofilter. Biofilters contain bacteria that break down fish wastes and decaying plant matter into nutrient-rich solutions.
• Water pump. This piece circulates water throughout the system and facilitates aeration. 
• Siphons/standpipes. Siphons drain water from the grow bed into the fish tank. 

The design of your Aquaponics system will depend on several factors, including: 

• Space. Availability of space may determine what type of system you should establish. Also, it’ll tell whether you can scale up your system or not. 
• Use. What’s the purpose of setting up your aquaponics system? Is it simply for home food production or for commercial use? Do you intend to utilize it for educational purposes? 
• Environment. Aquaponics requires a specific balance of environmental parameters such as temperature and pH. You should determine which aquaponics design will better fit your location.
• Plant species. What types of plants will you incorporate into your system? A plant’s nutrient and environmental requirements should match your fish species in the system. 
• Technical capabilities. Some designs may require more skills than others. Hence, it’s vital to know the expertise level that each aquaponics system requires for its setup and management.

Fish in an Aquaponics System

Depending on your location, you can rear either saltwater or freshwater fish in your aquaponics system.

Choosing the right fish species for your tank plays a key role in effective plant growth. The fish breeds should be well-suited for the environmental conditions in your farm and compatible with other species that you’ll incorporate into your unit.

Some of the most popular fish breeds for aquaponics:

• Tilapia. These are the most popular freshwater fish in Aquaponics, as they’re easy to keep and breed. Tilapias are hardy and adapt to fluctuating environmental conditions. The species’ incorporation in integrated farming has proven to be profitable for many farmers.
• Yellow Perch. These are edible and fast-growing freshwater fish that you usually find living in cold climates. However, yellow perch can adapt to varying pH levels. 
• Catfish. One of the best fish breeds to have if you’re a beginner in Aquaponics. They’re easy to manage and have a fast growth rate. Catfish can live in warm waters and have a pH range of 5.0 to 7.0.
• Koi. Koi fish are a sought-after ornamental breed. Apart from their aesthetic appeal, koi can survive in varying environmental conditions.
• Trout. These cold-water fish breed needs high levels of dissolved oxygen to survive. Trout are carnivorous and mostly feed on smaller fishes. Because they require intensive maintenance, trout-keeping isn’t well-suited for newbies.

Note: Different fish breeds have varying nutritional and environmental conditions. Always ensure that they are well-fed and live in a favorable environment. Be up-to-date with your state’s laws concerning fish importation if you’re planning to have exotic fish species in your unit.

Now that we’ve put the basics out of the way, let’s take a look at each aquaponics system. 

1. Media-Based Grow Bed

Also referred to as Flood and Drain, media-based grow bed is a popular aquaponics system for small-scale food production, as it doesn’t require much space. Moreover, newbies prefer this design due to its simplicity and cost-effectiveness. So, if you’re thinking of venturing into aquaponics, this might be the ideal starting point. 

Features of the Media-Based Grow Bed

A media-based grow bed system entails several fascinating features, including the grow bed, biofilter, flood and drain mechanism, and automatic siphons. It’s not surprising that it’s emerging as one of the most sought-after aquaponics models. 

Media-Filled Grow Bed

In this system, vegetables are planted in a grow bed. The bed is made of an inert substrate like gravel, expanded clay pebbles, or lava rock. It serves as the plant’s root (mechanical) support and microbial substrate.

Having a grow bed allows this system to grow all kinds of plants, including vegetables with bigger roots.

Biofilter

The grow bed is home to a colony of nitrifying bacteria that break down the fish wastes— consisting mainly of ammonia — into a form that plants can consume effectively. 

In media-based aquaponics, bacteria play the crucial role of being the system’s biofilter. Since no other filtration is needed, this lets farmers save on equipment costs.

Flood and Drain (Ebb and Flow) Mechanism

Most media-based grow bed systems utilize flooding and draining to fill the plant bed with nutrient-filled water. A water pump drives water from the fish tank into the beds and floods it. After the plants have taken up all the nutrients, the water is pumped back to the fish tank, draining the grow bed. 

Another method of feeding the plant bed involves pumping the water continuously without flooding or draining the bed. This way, the plants will always have access to nutrient-rich water. Besides requiring a smaller water pump, this method makes it easier to expand your grow bed.

The gravel or pebbles also serve the purpose of enhancing water filtration. Water returns to the fish bed after being purified mechanically and organically. Moreover, the spaces between this substrate provide enough space for the plant roots to take a firm hold. 

Automatic Siphons

The flood and drain layout uses automatic siphons to drain water from the grow bed. This design may also incorporate a water pump, a timer, and an indexing irrigation valve to control draining. The draining process usually occurs every 20-30 minutes of irrigation, allowing the plant roots to take oxygen in an optimal pattern. 

Advantages of the Media-Based Grow Bed System

The media-based system is best suited for small-scale farmers. They can easily fit in a backyard and other small spaces. But there are several advantages to the media-based grow bed system:

• It involves a simple and cost-effective design — ideal for newbies and small-scale farmers. 
• It has an efficient biofiltration system and solid filtration components. 
• Due to its excellent aeration, it’s compatible with most plant types, including vegetables and fruiting plants. 

Disadvantages of Media-Based System

Despite its amazing pros, the media-based grow bed system does have a few shortcomings. Its small scale can end up limiting some aspects of aquaponics.

• The system is hard to scale up, as the media substrate isn’t space-efficient and requires time and labor. It’s definitely not convenient for commercial use. 
• It’s labor-intensive due to its high maintenance and cleaning requirements. 
• High-quality media are costly. 
• The grow bed requires heavy hydroponics infrastructure. 
• The flood and drain method requires a large sump tank. 
• The substrate’s pore spaces are prone to clogging, which can lead to the plants not receiving enough oxygen. 

2. Nutrient Film Technique (NFT)

NFT is an aquaponics system that entails placing plants on vertical planes and horizontal pipes. Its high space efficiency is comparable to what you’d see in many hydroponic systems. NFT systems are also less labor-intensive and require minimal maintenance. 

Features of the NFT System

The nutrient film technique is ideally suited for commercial use. It’s easily scalable, and it can yield a higher output than media-based systems. Its minimal water requirements also make it the top choice for sustainable farming.

Horizontal Pipes

The nutrient film technique utilizes channels or gutters that are extruded from PVC pipes that are then placed horizontally. Their dimensions vary depending on the type of plant, but the most common measurements are about 4 to 9 inches (10-23 cm) in width and 1.5 to 4 inches (4-10 cm) in depth.

In NFT, a thin film of nutrient-rich water flows through these channels periodically. The plants’ roots are partially submerged into the water through perforations in the horizontal pipes, exposing them to the minerals and nutrients present in the water.

You can grow your plants in plastic cups and then place them in the perforated pipes. However, NFT isn’t ideal for plants with large roots, like tomatoes, cucumbers, or pepper. It’s better suited for leafy vegetables with a smaller root system, like spinach, basil, lettuce, and kale. 

Fish Tank

As in other aquaponics systems, the fish tank is a vital component. After feeding your fish, water containing their leftover food and wastes flows from the fish tank into the hydroponic system. Filtration must take place before the water leaves the tank, which is where the next component comes in.

Filtration Components

In NFT, it’s recommended to have a separate mechanical filter and biofilter. Since plants aren’t growing on a solid substrate like in media-based systems, it’s paramount to completely filter the waste coming in from the fish tank.

The biofilter is also made of air stones that provide a rich source of oxygen. These are usually packaged with nylon nets or bottle tops. But what makes these air stones vital is that they host a nitrifying bacteria colony. These bacteria break down fish wastes, converting it into a nitrogen form that plants can take as a nutrient. 

Apart from converting fish wastes, this extra step of filtration also helps minimize pipe clogging. It may still occasionally occur, though, especially if the gutters are on the thin side.

After passing through the biofilter, the water is pumped back to the channels containing the plants.

Irrigation Line

As we’ve explained earlier, NFT consists of perforated horizontal pipes that feed nutrient-rich water to the plants. In this layout, the irrigation line is made of tubes of about 5 to 8 inches (12-20 cm) in diameter. However, the specific measures may vary depending on the water source and biofiltration media in the system. 

Note that not all the water that leaves the fish tank ends up in the channels. After going through mechanical and biological filtration, some purified water goes back to the fish tank. Gravity helps the water flow from the pipes flow back down.

Because water flows continually in NFT systems, plants are exposed to a consistent stream of nutrients. When it leaves the plant gutters, the water returns to the biofilter and is then pumped back to the fish tank. As the fish tank overflows, the water flows through an exit pipe and then to the mechanical filters. 

Advantages of the NFT System

Nutrient film technique is an aquaponics layout that has modernized the application of hydroponics in integrated systems. Its advantages have attracted farmers who want to increase their output while taking up as little space as possible.

Here are the key advantages of NFT systems:

• The water film method ensures a continuous flow of water, oxygen, and nutrients.
• The system requires low amounts of water.
• It’s a scalable system. This makes it applicable for large-scale food production. 
• It is space-efficient and requires a few materials to set up, making it ideal for urban settings and commercial use. 
• The horizontal planting pipes are transferable and accessible. This makes harvesting the plants an easy task.
• It has fewer maintenance requirements. 
• It’s ideal for producing smaller, fast-growing vegetables and herbs such as Swiss chard, lettuce, and oregano. 

Disadvantages of NFT

NFT isn’t as popular as other aquaponics systems. The main reason is that this technique is only suitable for specific types of plants. Although you can adjust it to suit different types of crops, doing so will require more maintenance and, consequently, additional costs. 

Here are some of the disadvantages of NFT: 

• The design is inappropriate for large fruiting plants. Their massive root bases can be too heavy for the pipes. 
• The narrow pipes in this layout are susceptible to clogging from organic wastes. It requires regular cleaning and maintenance. 
• The plant roots hang in the air and don’t have as much contact with water. This may expose them to drastic temperature fluctuations. 
• NFT doesn’t incorporate a planting medium (substrate), and a good part of the plants isn’t exposed to air. Hence, the system requires a separate biofilter to break down nitrogenous wastes. 

3. Deep Water Culture (DWC) or Floating Rafts

Also referred to as the raft/float technique, deep water culture is perhaps the most stable aquaponics system. It involves growing plants suspended on rafts that float in nutrient-rich water. It’s highly efficient, making it suitable for commercial use. 

If you’re thinking about large-scale food production, DWC should be your go-to aquaponics system. Its stability, sustainability, and scalability make it spark more interest than other types of systems. However, it does require a high fish stocking density to keep the system running. 

Features of Deep Water Culture

DWC enhances plant growth rates as well as crop yields, which are both ideal qualities for a commercial setting. Its simple design and reliability are added advantages. Let’s have a look at what makes each part of this system so convenient.

Floating Rafts

Floating rafts are the most vital components of this aquaponics system. They can be of different materials, but polystyrene insulation is usually the top choice. The rafts are perforated to allow the plant’s roots to be submerged in the water. 

Rafts also contain net pots, which act like plastic cups to hold the plants. Thanks to recent technological advancement, these recipients are made of food-grade materials. Rafts are easy to set up, clean, and transfer.

DWC appears to resemble NFT in that they’re both media-less systems. However, there are some key differences that set them apart. For instance, NFT uses a thin water film, while DWC involves a much larger water volume. 

Biological and Mechanical Filtration

Since DWC is a media-less technique, plants lack a biofiltration medium. A framer will need to install a separate biofilter to convert nitrogenous wastes into plant-friendly nutrients. This inevitably drives up costs.

You’ll also need to include a mechanical filtration component when setting up the system. There are many designs you can choose from, but perhaps the most efficient route is to combine a swirl filter to sieve large wastes and a mesh screen for small wastes. After going through this mechanism, the biofilter will be able to act more effectively.

Fish Tank

DWC requires a large fish tank, as the system thrives with a large stock of fish. Since the technique involves a lot of water, you should also have higher fish feeding ratios. This will ensure that water maintains optimal nutrient levels.

Water flow dynamics in DWC are similar to those in NFT. Water containing fish wastes leaves the fish tank with the help of gravity and enters the mechanical filters. Then, it reaches the biofilter, where it’s pumped in two directions through valves in a “Y” connector.

Some of the purified water returns to the fish tank from the sump. The rest of the water flows into the canals where the floating rafts are suspended.

Once the plants have taken enough minerals, the water exits the canals and goes back to the sump. Then the cycle starts again as a pump drives water in the two directions. 

The water that goes back to the fish tank causes an overflow. An exit pipe lets the water go back into the mechanical filter. The downside of this design is that it’s possible for water containing wastes to find its way into the pipes.

Water Supply

Deep Water Culture requires a high water volume to sustain its large fish density. Since the system also involves submerging plants in nutrient-rich water, the water flowing into the canals should be deep enough to facilitate it. The ideal water depth ranges from 4 inches to 3 feet (10-90 cm). 

Ideally, this water flow should be ensured with a sustainable design. Farmers can choose different layouts depending on: 

• Availability of construction materials
• Labor requirements
• Structure durability and stability
• Set up costs
• The preferred volume of the system and availability of space

The ‘Cascade’ layout is a simple and effective setup that both hobbyists and large-scale farmers can consider. In this design, water is distributed in such a way that only one inlet serves all the tanks. This is made possible because the outlet of one tank becomes the inlet of the next tank, and so on, to form a continuous water flow. 

Root Aeration Devices

One of the drawbacks of Deep Water Culture is that submerging the plants limits aeration. This makes oxygen demand high, and even more so because of the high densities of plants and fish. Farmers may need to take extra steps to ensure that the water is properly oxygenated.

To address this issue, you can incorporate root aeration devices into the system. These will minimize stagnation and oxygen deprivation around the roots. Diffuser air stones are the most common items used in this technique. Place the air stones at intervals of 4 feet (1.2 meters) under the floating beds for maximum aeration. 

DWC Grow Canals

Unlike in NFT systems, you can have canals of different lengths in DWC. However, it’s usually recommended to have longer canals, as the system uses a lot of water, and the plants need a continuous supply of nutrients. Having standard widths will also facilitate a seamless water flow. 

You can also have some freedom in deciding the width of your canals. Wide canals give more space to the plants, while narrow ones increase water speed and help more nutrients reach the plants.

Lastly, you can choose among several types of materials to use for the canals. These are some of the most recommended materials: 

• Fiberglass 
• IBC plastic 
• Wood  
• Concrete 

Concrete canals should have a coating of food-grade waterproof sheeting to prevent the leaching of harmful substances from concrete into the system. 

Advantages of DWC

Deep Water Culture is a technique of choice among many aquaponics hobbyists and large-scale farmers. The system is versatile and reliable yet simple and cost-effective. 

Let’s have a look at its advantages:

• It’s scalable, making it suitable for commercial food production. 
• It has a higher food yield volume than other systems. 
• It has a low initial cost.
• It’s easy to clean and maintain.
• There’s minimal water loss through evaporation.
• Plants have a continuous supply of minerals. 
• Plants aren’t exposed to temperature fluctuations or poor water quality. 

Disadvantages of DWC

Despite its benefits, DWC has some shortcomings. The system is ideal for large-scale and commercial use. Hence, it may not be well suited for newbies in aquaponics. 

DWC cons include: 

• It requires a large space and a high water volume. 
• It’s better suited for warmer climates, as it’s expensive to frequently heat the high water volume. 
• Since plants are submerged, they usually require root aeration devices. 
• A separate biofilter is required. 
• A poor design may turn the system into a mosquito breeder. 
• DWC requires heavy hydroponic structures to support all the plants. 
• The system is best suited for plants with smaller root bases, including vegetables and herbs.