What is the Nutrient Film Technique (NFT) in Aquaponics?
The Nutrient Film Technique (NFT) in Aquaponics is a method in which the plants are grown in a long narrow channel. NFT is a hydroponic growing technique that is adapted to aquaponics because of its simple yet effective design that works well in many environments.
In NFT, a thin film of water flows continuously down each channel, providing the plant roots with water, oxygen, and nutrients. When the water reaches the end of the channel, it normally flows back to the fish tank using gravity to the sump tank and sometimes to the fish tank if you are running a system without a sump tank and where the NFT is higher in elevation than the fish tank. (1)
Similar to the raft system and media-based system, NFT uses a water pump to deliver nutrients to the plants. This system requires a separate filter to clear the water of solids and biological waste before it enters the NFT system, otherwise the roots can be blocked out from getting oxygen.
Nutrient Film Technique systems are primarily used in cultivating greens that have smaller roots systems. NFT is commonly used in the commercial aquaponic system but can also a hobby system as long as the water is filtered before it is used in the NFT channels.
Additional Bio-Filtration In NFT
In an NFT system, a biofilter is very important because the system by itself does not have enough surface area to provide a habitat for the bacteria. The bacteria converts ammonia into nitrites and then into nitrates (2).
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 channels for the plants (3).
Water travels from the fish tank → solid filter → biofilter → NFT channels → fish tank.
Water Flow in NFT
The water flows from the fish tank through a solid filter and into the biofilter. From the biofilter, the water is pumped in two directions through a Y connector, where some water is pumped directly back into the fish tank. The remaining water is pumped and distributed equally into the NFT grow channels, allowing plants to absorb its nutrients. On exiting the growing channels, the water flows back to the biofilter, where again, it is pumped into the fish tank or grow pipes, completing the cycle.
NFT Grow Channels
NFT uses channels (usually PVC pipes) laid out horizontally to grow plants. These pipes can be arranged in many patterns and can make use of vertical spaces, walls, fences, and overhanging balconies. The water is pumped from the biofilter into each pipe with a small equal flow, creating a shallow stream of nutrient-rich water flowing in the bottom. The grow channels contain several holes along the top of pipes, which is where the plants are placed. The film of water at the bottom of the pipes ensures that the roots receive a large amount of oxygen at the root zone for moisture and nutrition.
The grow channel length can be between 1 and 12 meters, as nutrient deficiencies can occur in plants towards the end of pipes that are longer than 12 meters because the first plants have already removed the nutrients. To ensure the water flows through the pipes with ease, there should be a slope of about 0.4 inches of pipe length. White pipes are recommended because they reflect the sun’s rays, keeping the inside of the pipes cool (4).
Planting on Grow Pipes
In NFT aquaponics growing, holes are drilled into the pipes that match the size of the net cups. Seedlings are placed into a plastic net cup, which is then placed in the grow pipes. 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 further and support the plants (5).
Strength And Weaknesses of NFT Aquaponics Systems
- Roots are highly oxygenated - The roots receive plenty of air because part of the root is exposed. This helps in preventing root rot. (3)
- Constant Flow of Water - The constant 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 constant movement of water helps reduce the risk of fungal growth.
- The roots can clog the channels - Roots dangling in the water are great for the health of the plants. 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. (3)
- 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 they will wilt or die rapidly. (3)
- 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 a Nutrient Film Technique System
Many plants can be grown successfully in NFT systems, but plants that have shallow roots, are lightweight, fast-growing, require less care can adapt more quickly to NFT systems. For your system to succeed, it is important to know the best plants to grow in an NFT aquaponics system.
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. (5)
Just like any other aquaponics system, NFT aquaponics systems can present some problems, particularly in operation. However, even if difficulties arise, proper planning, regular monitoring, and good maintenance can overcome them. (5)
When you plan your NFT aquaponics system, it is important 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. Take time to regularly monitor your system temperature regularly and ensure that the roots are not exposed to light to prevent algae growth in the system.
Proper maintenance is essential 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 are the plants' roots themselves, stopping the flow of water, so they should be checked regularly (5).
Nutrient Film Technique Aquaponics Systems, just like the other aquaponics systems, NFT 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. Feel free to leave your comment below and join our mailing list to get aquaponics updates.