Nutrient Film Aquaponic Unit – Step by Step Description


Aquaponics is the integration of recirculating aquaculture and hydroponics in one production system. The Nutrient Film Technique (NFT) is one of the three common methods of aquaponics being utilized at the present, suitable especially for small–scale commercial environments. It is often utilized in vertical growing systems where floor space is limited. This technology provides a detailed explanation of the main components and a step by step guide to construct a small–scale aquaponic unit using this method.


In Nutrient Film Technique (NFT), a thin layer of nutrient–rich water is circulated through horizontal pipes. Plants are within net pots hat are suspended within holes at the top of the pipes so the roots are in contact with the water. The water supplies nutrients to the plants that then develop extensive root systems within the pipes. The plant stems and leaves then grow out from and around the pipes.

Components of the Nutrient Film Aquaponic Unit (NFT)

1. Water flow

In the nutrient film technique unit described in this technology, water flows by gravity from the fish tank, through the mechanical filter and into the combination biofilter/sump. From the sump, the water is pumped in two directions through a “Y” connector and valves. Some water is pumped directly back to the fish tank. The remaining water is pumped into a manifold that distributes the water equally through the NFT pipes. The water flows, again by gravity, down through the grow pipes where the plants are located. On exiting the grow pipes, the water is returned to the biofilter/sump, where again it is pumped either into the fish tank or grow pipes. The water that enters the fish tank causes the fish tank to overflow through the exit pipe and back into mechanical filter, thus completing the cycle.

2. Filtration

Two types of filters need to be added when using this technique: first, a physical trap to catch the solid wastes, and then a biological filter for nitrification. The designs described in this technology use a mechanical swirl filter to trap particulate wastes, with periodic venting of the captured solids. On exiting the swirl filter, the water passes through an additional mesh screen to trap any remaining solids and then reaches the biofilter. The biofilter is well oxygenated with air stones and contains a biofiltration media, usually Bioballs®, nylon netting or bottle caps, where the nitrifying bacteria transform the dissolved wastes. With insufficient filtration, the NFT units would clog, become anoxic and exhibit poor growing conditions for plants and fish alike.

3. Nutrient film technique (NFT) grow pipes

NFT then employs the use of plastic pipes laid out horizontally to grow vegetables using the aquaponic water. Where possible, use pipes of rectangular section with width larger than height, which is standard among hydroponic growers. The reason lies in a larger film of water that hits the roots with the scope of increasing the nutrient uptake and plant growth. One of the benefits of the NFT is that the pipes can be arranged in many patterns and can make use of vertical space, walls and fences, and overhanging balconies

   How does it work?  The water is pumped from the biofilter into each hydroponic pipe with a small equal flow creating a shallow stream of nutrient–rich aquaponic water flowing along the bottom. The grow pipes contain a number of holes along the top of the pipe into which the plants are placed. As the plants start to consume the nutrient–rich water from the stream, they begin to develop root systems inside the grow pipes. At the same time, their stems and leaves grow out and around the pipes. The shallow film of water at the bottom of each pipe ensures that the roots receive large amounts of oxygen at the root zone along with moisture and nutrition. Keeping a shallow stream allows the roots to have a larger air exchange surface. The water flow for each grow pipe should be no greater than 1–2 litres/min. The flow rate is controlled from the Y–valve, with all excess water flow returned to the fish tank.

  Grow pipe shape and size: It is wise to choose a pipe with the optimum diameter for the types of plants grown. Pipes with a square cross–section are best, but round pipes are more common and totally acceptable. For larger fruiting vegetables, 11 cm diameter grow pipes are needed while fast–growing leafy green and small vegetables with small root masses only require pipes with a diameter of 7.5 cm. For small–scale polyculture (growing many types of vegetables) 11 cm diameter pipes should be used. This avoids plant selection limitations because the small plants can always be grown in the larger pipes, although there would be a sacrifice in planting density. Plants with extensive root systems, including mature older plants, can clog smaller pipes and cause overflows and losses of water. Be especially mindful of tomatoes and mint, as their massive root systems can easily clog even large pipes.

The grow pipe length can be anywhere between 1 and 12 m. In pipes longer than 12 m, nutrient deficiencies can occur, especially  in plants towards the end of the pipes because the first plants have already stripped the nutrients. A slope of about 1 cm/m of pipe length is needed to make sure the water flows through the whole pipe with ease. The slope is controlled by using shims (wedges) on the side away from the fish tank.

PVC pipes are recommended because they are usually the most commonly available and are inexpensive. White pipes should be used as the colour reflects the sun’s rays, thereby keeping the inside of the pipes cool. Alternatively, square or rectangular hydroponic pipes with dimensions 10 cm width × 7 cm height are recommended. Professional hydroponic pipes for commercial growers are typically this shape, and some growers use vinyl fence posts.

  Planting within the grow pipes

The holes drilled into the hydroponic pipe should be 7–9 cm in diameter, and should match the size of the available net cups. There should be a minimum of 21 cm between the centre of each plant hole to allow adequate plant space for leafy greens and larger vegetables. Each seedling is placed into a plastic net cup, which is then in turn placed within the grow pipe. This provides physical support for the plant. The net cups are filled with general purpose hydroponic media (volcanic gravel, rockwool or LECA) around the seedling. If desired, a 5–10 cm length of 5 cm PVC pipe can be placed inside the net cup as further balance and support to the plant.

If plastic net cups are not available or are too costly, it is possible to use regular plastic drinking cups, making sure to add many holes to the plastic drink cup so the roots have plenty of access into the grow pipe. Other growers have had success with flexible, open–cell foam to support the plants within the grow pipe. If none of these options is available or desired, it is possible to transplant the seedlings directly into the pipes, particularly rectangular pipes. Seedlings can be transplanted with their germination medium, which will wash away into the system or the roots can be carefully rinsed, which keeps medium out of the system but can increase the transplant stress. Nevertheless, it is preferable to use net cups filled with media.

When initially planting the seedlings into the pipe, make sure the roots can touch the stream of water at the bottom of the pipe. This will ensure that the young seedlings do not become dehydrated. Alternatively, wicks can be added that trail into the water stream. In addition, it is advisable to water the seedlings with aquaponic water one week prior to transplanting them to the unit. This will help mitigate against transplant shock for the plants as they become accustomed to the new water.

Step by Step guide to construct a NFT unit

Materials: A detailed list of materials and tools needed for the construction of a media bed unit is attached at the bottom of this section (please see further reading, page 228)

1. Preparing the fish tank

– Please follow the same procedures explained in the Media Bed Aquaponic Unit

2. Preparing the mechanical separator and biofilter

–Take two blue barrels (200 litre) (Figure 1) and cut out the shapes marked in the figures below (Figures 2–4) using the angle grinder. Afterwards, wash both barrels with soap and warm water thoroughly and leave to dry in the sun for 24 hours.

– The cut pieces of both barrels can also be used as barrel covers. They can be fixed to the top of the barrel using cable ties (see Figures 5–6).

3. Barrel No. 1 – mechanical separator

A. Inlet pipe from the fish tank.

B. Drainage pipe at the bottom of the mechanical separator.

C. Outlet pipe into the biofilter.

A. Inlet pipe from the fish tank

 – Drill a hole (50 mm) using the 50 mm circular drill bit at the top surface of the barrel and slide in the fish tank exit pipe (Figures 8–9).


– Extend the exit pipe of the fish tank to 30 cm above the bottom of the mechanical separator container. Attach a PVC elbow (50 mm) to the bottom of the exit pipe so the water flows tangentially to the container forcing the water to circulate (Figure 10).

B. Drainage pipe at the bottom of the mechanical separator

– Next, take a length of PVC pipe (50 mm) and cut 2–3 mm horizontal slits along the entire length using the angle grinder (Figure 11). Drill a hole (57 mm) on the outside of the barrel, 5 cm above the bottom, and insert a uniseal (50 mm) (Figure 12). Slide the drain pipe (50 mm PVC pipe cut with slits) through the uniseal and connect a PVC elbow (50 mm) to the end of the pipe outside the barrel. Finally, attach another PVC pipe (50 mm) that is 60–70 cm in length to the elbow and make sure that the end of the pipe is above the maximum water level of the barrel (Figure 13). The slits on the drainage pipe will allow solid waste to enter it and be flushed out by reclining the other vertical pipe attached outside of the barrel and pouring out the water from its end.

C. Transfer pipe connecting the mechanical separator to the biofilter.

 – Take a 65 cm length of PVC pipe (50 mm) and cut the same horizontal slits as above (3.3) for only the first 25 cm of the pipe using the angle grinder (Figure 14). Seal the slotted end of the pipe (50 mm) using a PVC endcap/stopper (50 mm). Next, drill a hole (57 mm) with the 57 mm circular drill bit 70 cm from the bottom of the barrel, and insert a uniseal inside the hole. Slot the transfer pipe (50 mm) through the uniseal, making sure the end with 25 cm slits is completely inside the mechanical separator barrel (Figures 15–16).

4. Barrel No. 2 – biofilter

A. Inlet pipe from the mechanical separator (Figure 17).

B. Water outlet from the water pump.

C. Drainage tap.

25 mm drain tap

– Drill a hole (25 mm) at the very bottom of the biofilter barrel and insert a barrel connector (V type, 25 mm) into the hole and fasten it tight. Attach a tap (25 mm) to the barrel connector on the outside of the barrel making sure the connecter is wrapped with Teflon to make a water tight seal (Figure 18). The tap is used to flush out any solid waste accumulating at the bottom of the biofilter container.

Inlet pipe from the mechanical separator

– Drill a hole (57 mm) using the 57 mm circular drill bit 70 cm from the bottom of the barrel and insert a uniseal in the hole (Figure 19). Place the biofilter barrel adjacent to the mechanical separator barrel. Take the 65 cm PVC pipe length already attached to the mechanical separator barrel and slot it through the uniseal in the biofilter barrel as well. Now, both barrels are joined together using this transfer pipe (Figure 20).

Preparing the solids capture bucket

– Drill a 50 mm hole in the 20 litre bucket 5 cm below the top rim of the bucket (Figure 21)

– Drill at least 20 holes (8 mm diameter) into the bottom of the bucket using an 8 mm drill bit to allow water to drain into the biofilter (Figure 21).

– Insert and slide the bucket along the 65 cm transfer pipe inside the biofilter (the same 65 cm pipe that connects both filter barrels (Figures 22–23)

– Drill a 20 mm hole into the transfer pipe and insert 6–10 cm of PVC (20 mm) (Figure 23) to prevent the solids capture bucket from sliding off the transfer pipe.

 – Place filtration media (in this configuration we use volcanic gravel but perlon, sponge or other filters may be utilized) inside the bucket to capture any remaining solid or suspended waste (Figure 24).

– Fill the biofilter with biofilter medium (Bioballs or bottle caps).

5. Positioning the NFT pipes

The materials needs for this section are as follows:

  • 48 concrete blocks
  • 1 m wood length (30 mm thick) × 1
  • 1 m wood length (20 mm thick) × 1
  • 1 m wood length (10 mm thick) × 1

– Place the concrete blocks according to the distances in Figure 25. Each stand is made of 8 blocks (two columns, each column 4 blocks high. Place the wood lengths on to the blocks: place the 3 cm thickness length along the column of blocks furthest away from the tank, the 2 cm thickness length on the middle columns and the 1 cm thickness length on the closest columns. This arrangement will create a small slope allowing the water to easily flow through the pipes and return to the biofilter barrel (Figure 25).

6. Connecting the NFT pipes and communal drain

The materials needs for this section are as follows

  • 3 m of PVC pipe (110 mm) × 5
  •  PVC elbow (110 mm) × 2
  •  PVC T connector (110 mm) × 4
  •  PVC endcap/stopper (110 mm) × 5
  • Rubber washer (110 mm) × 15
  • Natural soap

– Connect the pipe system according to Figure 27. Make sure that each pipe and pipe fitting has a lubricated rubber seal fitted inside using the natural soap as a lubricant (Figure 26).

7. Marking the plant holes

–Place the NFT pipes on top of the blocks and wood lengths and fit the five end caps (110 mm) to the ends of the pipe furthest from the fish tank (Figure 30). One effective method for marking the plant holes is to stretch and secure a thin piece of rope along the top of each pipe to mark uniform distances accurately.

– Mark a point every 25 cm along the rope (Figure 29) which will be the centre point for the holes. Drill the holes (Figure 33) according to the size of the net pots. For optimal plant growing space, follow the triangular pattern shown in Figures 28 and 31.

–Finally, drill 20 mm holes, 7 cm from the ends of the pipe farthest from the fish tank to allow water to enter the NFT pipes (Figure 34). Secure the NFT pipes to the wood length using plastic cable ties (Figure 35).

8. Connecting the end of the grow pipes back to the biofilter

– Take a PVC straight coupler/connecter (110 mm) and attach it to the final PVC elbow (110 mm) of the common gutter of the NFT pipes (Figure 27), which is made with a series of PVC T connections (110 mm). Then, attach a PVC reducer (110–50 mm) to the PVC straight coupler/connecter (110 mm). This communal drain must connect to the biofilter. Drill a 50 mm hole on the outside of the biofilter, 10 cm lower than the bottom of the grow pipes. Fit a PVC elbow (50 mm) into this hole. Use PVC pipe (50 mm) to connect the elbow (50 mm) to the reducer (110–50 mm) allowing the water to flow from the NFT pipes back into the biofilter barrel (Figures 36–38).

9. Installing the distribution piping for each NFT pipe

The materials needs for this section are as follows:

  • PVC “push on” taps (20 mm) × 5
  • PVC “push on” T connectors (20 mm) × 4
  • PVC “push on” elbow connectors (20 mm) × 2
  • Polyethylene pipe (20 mm)
  • PVC adapter (20 mm – ¾ inch × 1
  • PVC elbow female connector (25 mm – ¾ inch) × 1
  • Plumber’s tape (Teflon)

– Connect all of the pipe and fittings according to Figures 39 and 40.

10. Adding the submersible pump

– For this unit, the submersible pump is placed at the bottom of the biofilter barrel (Figures 41a and 41b). Water is pumped from there to two locations: the NFT pipes and the fish tank. 80–90 percent of the water flows to the fish tank while 10–20 percent flows into the NFT pipes. The taps are used to control the water flow at each location.

11. Pumping to the fish tank

– Connect the submersible pump to a length of polyethylene pipe (25 mm) using a PVC adaptor, female (25 mm – 1 inch), or any connection that fits the pump. The polyethylene pipe (25 mm) should be at least 1 m long. Place a PVC T connection (25 mm) at the end of the pipe to allow water to flow to the fish tank and the NFT pipes (Figures 42–43).

 – Attach a PVC pipe (25 mm) to one end of the T connection (Figure 42) long enough to reach the fish tank (Figure 44). Use a flexible pipe, if possible, to remove the need for additional connectors, which would reduce the pumping capacity of the pump. Attach a tap (25 mm) to the end of the pipe to control the incoming water flow into the fish tank (Figure 44).

 Next, take about 4 metres of PVC pipe (25 mm) and attach to the other end of the PVC T connector (25 mm) coming from the water pump pipe inside the biofilter. Attach this pipe (25 mm) to the distribution manifold through the PVC elbow female connector (25 mm – 3/4 inch) seen in Figure 40, which will supply water to each NFT pipe (Figure 44).

12. Electric box + air pump

Place the electric box in a safe place higher than the water level and shaded from direct sunlight (Figure 45). Make sure it is still water proof after plugging in the water and air pump plugs, and put the air stones inside the fish tank (Figure 46).

13. Final checks

All parts of the system are now in place. Before adding ammonia for cycling, fish or plants, fill the fish tank and both filters with water and run the pump to check for any leaks in the system. If leaks appear, fix them immediately (Figures 47–49). The following steps show this process.

Mechanical separator drainage check (Figures 50–52).

  • Fill the biofilter with media and water (Figures 53a and 53b).
  • Fill the mechanical separator with water (Figure 54).
  • Mechanical separator and biofilter (Figure 55).

  • Tighten the plumbing connections.
  • Check all uniseals and taps for both filters.
  • Re–apply Teflon to threaded connections.
  • Make sure all valves are in their ideal position.
  • Finally, check the flow rate of the water flowing into each NFT pipe. The flow rate can be measured with a stopwatch and an empty 1 litre plastic bottle. A flow rate of 1–2 litres/minute, which is the standard in NFT pipes, should fill the bottle in 1 minute (1 litre/minute) or 30 seconds (2 litres/minute) (Figure 56). Once all the leaks are fixed and the water is flowing smoothly through all components, it is possible to start cycling the unit using ammonia.

14. Planting – making the planting cups

– For planting, follow what is shown in the following figures. Make sure the plant cup has enough holes to allow the root system to grow out into the pipe but also to prevent the growing medium from falling out. A plant cup made from a net cup and 10 cm of PVC pipe (50 mm) (Figures 57–59). A plant cup made from simple plastic/paper cups and a plastic bottle (Figures 60 and 61). Plant roots clearly visible (Figures 62–66).


This technology comes along with other practices about Aquaponic unit:

1.   Designing an Aquaponic unit

2.   Media Bed Aquaponic Unit - Step by Step Description

3.   Nutrient Film Aquaponic Unit – Step by Step Description

4.   Deep Water Culture Aquaponic Unit – Step by Step Description

5.   Management of the Aquaponic Systems

Further reading

Small-scale aquaponic food production - Integrated fish and plant farming (FAO, 2014):

7 rules-of-thumb to follow in aquaponics:

Created date

Wed, 03/06/2015 - 16:21


Fisheries and Aquaculture Department (FI) in FAO

Fisheries and aquaculture have the capacity – if supported and developed in a regulated and environmentally sensitive manner – to contribute significantly to improving the well-being of poor and disadvantaged communities in developing countries and to achievement of several of the Millennium Development Goals, especially those related to poverty reduction and food and nutrition security, environmental protection and biodiversity. As part of a long-term strategy, the FAO Fisheries and Aquaculture Department (FI) is envisioning a world in which responsible and sustainable use of fisheries and aquaculture resources makes an appreciable contribution to human well-being, food security and poverty alleviation. In this regard, FI works towards strengthening global governance and the managerial and technical capacities of members and to lead consensus-building towards improved conservation and utilization of aquatic resources. The activities of FI reflect the main FAO mandate of managing knowledge and information, assuring a global neutral forum for Members and providing technical assistance at national, regional and global levels.

In addition, the FAO Fisheries and Aquaculture Department undertakes capacity development activities for marine and inland fisheries as well as aquaculture. These include training at different levels, preparation of training and extension materials for general or targeted training, awareness raising through workshops, and collaboration with partner training institutions.  The FI is also involved in the development of appropriate technical guidelines and the promotion of participatory approaches in sustainable and responsible aquatic resources management, including gender aspects.

The Aquaculture Branch of FI (FIAA) is particularly responsible for providing technical assistance towards sustainable and responsible aquaculture development and management in support of improving food and nutrition security and alleviating poverty, globally.

The Products, Trade and Marketing Branch (FIAM) of the Fisheries and Aquaculture Department of FAO, assists FAO member countries on all aspects related to post-harvest. FIAM provides technical assistance in areas such as marketing, trade, handling and processing and preservation of fish products, food safety and nutrition. As such, FIAM supports activities along the value chain aiming at a sustainable supply of fish and fishery products in the market, while securing greater benefits for actors in the value chain. FIAM has broad experience in the field of promotion fish consumption, through the dissemination of knowledge on the nutritional value of fish and fishery products, including the promotion of good hygienic practices at any level of the supply chain (on board canoes/vessels, landing sites, aquaculture farms, factories and sales points).  Local fishermen and processors are assisted to adapt best practices in order to reduce food losses and waste, and to promote an optimal use of their fishery by-products, improving their returns, minimizing the environmental impacts and contributing to food security. Finally, as fish and fishery products are among the most traded food commodities worldwide, FIAM coordinates the implementation of Globefish, a programme collecting and disseminating information on markets and fish trade. Globefish produces a number of publications including fish price reports (European Fish Price Report), market studies (GLOBEFISH Research Programme) and trend analysis (GLOBEFISH Highlights).


Contact person: 
Aquaculture Branch of the Fisheries and Aquaculture Policy and Resource Division
Contact email: 
Contact person: 
Alessandro Lovatelli (Aquaculture Branch)
Contact person: 
Aina Randrianantoandro (Products, Trade and Marketing Branch)