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What is the Nutrient Film Technique (NFT) in Aquaponics?

The Nutrient Film Technique (NFT) is a hydroponic growing technique adapted to aquaponics because of its simple yet effective design that works well in some environments. This method uses horizontal pipes (usually PVC pipes) with shallow streams of nutrient-rich water flowing through it. Plants are planted in the holes in the top of the pipes and are able to utilize this thin film of nutrient-rich water. 

Nutrient Film Technique systems are primarily used in cultivating greens that have small root systems. NFT is popular for commercial aquaponics because it is more viable than the other aquaponics methods. This technique is also more useful in urban places where space and food production are considerations. However, it is more expensive to set up and is not suitable in locations that do not have enough access to suppliers.

Nutrient Film Technique of Aquaponics

How Nutrient Film Technique Works

In NFT, water is pumped or flows by gravity through the mechanical filter and into the biofilter or sump tank. Some water is pumped directly into the fish tank from the sump tank, while the remaining water is pumped and distributed through the NFT pipes equally. Then water flows again by gravity down through the grow pipes where the plants are planted. Upon exiting the grow pipes, the water is returned to the biofilter or sump and then returned into the fish tank or grow pipes. The water that enters the fish tank causes the tank to overflow through the exit pipe and back into the mechanical filter, completing the cycle.

Unlike the media-based system, the Nutrient Film technique does not require a flood period because the water in NFT flows consistently from the fish tank. The grow pipes contain several holes on the top of the pipe into which the plants are placed and grow. The plants will begin to develop root systems inside the grow pipes once the plants start to consume the nutrient-rich water. The shallow film of water at the bottom of each pipe ensures that the roots receive a large amount of oxygen.

Mechanical And Biological Filtration In NFT

In an NFT system, mechanical and biological filtration is very important because it does not have enough surface area to provide a habitat for the bacteria. This is why mechanical and biological filters need to be constructed to serve as a physical trap to catch solid wastes and biological filters for nitrification.

The biofilter is usually a tank or barrel that holds a porous medium that is heavily aerated and should be situated after the fish tank and solid filter before the water returns into the plants' channels. 

Water travels from the fish tank → solid filter → biofilter → NFT channels → fish tank.

NFT Grow Pipes

Following the filtration methods mentioned above, NFT uses plastic pipes (usually PVC pipes) laid out horizontally to grow plants using the water in the aquaponics system. The pipes can be arranged in different patterns and can make use of vertical space, walls, fences, and overhanging balconies.

The water is pumped from the biofilter into each pipe with a small equal flow, creating a stream of shallow nutrient-rich water flowing along the bottom. As plants consume the nutrient-rich water from the stream, they develop a root system inside the grow pipes. Keeping a shallow stream of water ensures that the roots receive large amounts of oxygen at the root zone. 

Grow Pipe Shapes And Size

In NFT, pipes with a square cross-section are best, but most aquaponics farmers use the round pipes because it is readily available in most locations. It is advisable to choose a pipe with the optimum diameter for the types of plants grown. For larger fruiting plants, use an 11 cm diameter grow pipe, while for fast-growing leafy green and small vegetables with small root mass, use a 7.5 cm diameter grow pipe. 

Planting In the Grow Pipes

Holes are drilled into the grow pipes (7-9 cm diameter), and these holes should match the size of the net cups used. There should be at least 21 cm between the center of each plant to allow adequate plant space. Seedlings are placed in a plastic net cup and then placed in the grow pipe's hole. The net cups will provide support to the plants. A space of about 8 inches between each plant is recommended to allow enough plant space for the plants. Grow media like clay pebbles or gravel can be placed around the seedlings in the net cups to balance and support the plants. For more detailed planting instruction read, How To Start Planting In Aquaponics.

NFT Grow Pipes

Strength And Weaknesses Of NFT

Strengths

  • Roots are highly oxygenated - The roots receive plenty of air because part of the root is exposed—these help prevent root rot. 
  • Constant Flow of Water - The continuous flow of water in the system helps prevent the buildup of solids on the roots and ensures that the nutrient-rich water is always available for the plant, increasing their growth and health.
  • Constant flow reduces fungal risk - The continuous movement of water helps reduce the risk of fungal growth. 

Weaknesses

  • The roots can clog the channels - Roots dangling in the water are great for the plants' health. However, as the plants grow, bigger roots can block the channels, preventing the water from getting to the rest of the plants, which may cause nutrient deficiency for the plants.
  • Water temperature fluctuations- The water that is pumped through the channels can quickly cool down or heat. This is because the film of water running through the NFT channels is very thin, making it subject to temperature fluctuations.
  • Pump failure can destroy yield - If the pump fails, the plants cannot have access to the water and will wilt or die rapidly. 
  • Can only grow limited plants -Leafy greens and small vegetable plants do well, but larger plants with large root systems are not well suited for NFT.

Plants To Grow In The Nutrient Film Technique

Many plants can be grown successfully in NFT systems, but plants with shallow roots are lightweight and fast-growing, require less care, and adapt more easily to NFT systems. Some of these plants are lettuce, chard, basil, mint, sage, and mustard. Choosing plants that grow the best in your system will ensure the success of the system.

Some plants like tomatoes, peppers, strawberries, and smaller varieties of eggplants can also be grown in NFT systems, but they will require extra care and support.

Root vegetables like carrots, corn, squash, cucumbers, melons, and trees are plants that should be avoided in NFT as they grow tall, spread considerably, or produce heavy fruit.

Nutrient Film Technique Tips

Like any other aquaponics system, NFT aquaponics systems can present some problems, particularly in the operation of a new system. However, even if difficulties arise, proper planning, regular monitoring, and good maintenance can overcome them.

When you plan your NFT aquaponics system, it is essential to consider how the setup will differ from other aquaponics systems. The shallow trays and the absence of growth media require proper planning to ensure success. 

Without growing media, root temperature is hard to maintain, especially if your area is exposed to rapidly changing temperatures. You should regularly monitor your systemtemperature and ensure that the roots are not exposed to light to prevent algae growth in the system.

Good maintenance is very important in NFT aquaponics systems. The two main components that should be checked regularly are; 

1) the water pump that brings water to the system. If the pump stops working, you could easily lose your entire crop. 

2) Clogging can also affect your system. The most common cause of a clog in NFT systems is the plants' roots themselves, stopping the flow of water, so they should be checked regularly.

Conclusion

Nutrient Film Technique Aquaponics Systems, just like the other aquaponics systems, offer many advantages and disadvantages. The important thing to remember in choosing an aquaponics system is that everything starts with trial and error. Have fun and don't be afraid to experiment. Difficulties always arise, but they can be overcome through proper planning, monitoring, and regular maintenance. Thank you for reading our article and feel free to leave your comment below.

 

2 Responses

Manie R

Manie R

July 27, 2021

Good day

Are there any calculations or ratios available for designing NFT aquaponics systems, like plants/fish or plants/tank size ratios etc? I tried Google searching this, but I can only find calculations for growbed based aquaponics systems?

Kind Regards
Manie R

Manoraj Govindraj

Manoraj Govindraj

May 24, 2020

Very excellent article. Thank you very much. I guess the motor / water needs to be continuously running 24/7. In case of power failure, ups is compulsory.

Thank you very much once again.
Bangalore. India.

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