Fact Sheet FS1351
New Jersey farmers, with support from the New Jersey Agricultural Experiment Station, have long been at the forefront of adopting new technologies and innovations in agriculture. Aquaponics—the combination of recirculating aquaculture and hydroponics—is a relatively new form of agriculture practiced in parts of the United States and other countries1,2. It is gaining attention in New Jersey with small-scale operations springing up across the state since 2015. International surveys of aquaponics farmers have found that the majority are producing plants like salad greens and basil as well as fish, like tilapia (Oreochromis species), ornamental fish (e.g., koi, goldfish, tropical fish), and catfish (order Siluriformes)1,2.
There will be an inevitable increase in demand for food to feed a growing global population. Trends indicate that more people are interested in purchasing food and food products that are locally grown through sustainable farming practices. Many farmers have accepted this challenge with alternative crops and modern production techniques, including a handful of growers in the Garden State who are producing crops by employing aquaponics systems. This fact sheet introduces the concepts, practices, benefits, and challenges of aquaponics for those interested in learning more about the subject or potentially starting an aquaponics farm. The Resources list below offers more detailed information on the topics covered in this fact sheet.
What is Aquaponics?
Aquaponics is the combination of recirculating aquaculture (the growing of fish or shellfish) and hydroponics (growing plants in water without soil) (Figure 1). In its basic form, aquaponics utilizes fish grown in a recirculating tank (Figure 1A and Figure 1B), with waste products then piped to a settling tank or solids filter (Figure 1C) where any solid materials are separated from the water. From there, the water flows to a biofilter containing microorganisms such as nitrifying bacteria that convert the ammonia, which is excreted by the fish, into nitrate nitrogen (Figure 1D). This nutrient-rich water is then piped to a tank where plants float (Figure 1E) with their roots dangling in the solution to take up these nutrients. During their growth, the plants reduce the amount of nutrients in this water, which is finally pumped back to the fish tank to repeat the process. This type of "closed" system is flexible in its design and can be scaled for use by small hobby growers or larger commercial operations (Figure 2).
Fish Culture Tanks
The culture tanks are where the fish live and grow, either for their entire lives or to a desirable market size if intended for sale. As with an aquarium or a backyard pond, the size of the tank will depend on the size of your system and the fish being grown. Larger fish will need larger tanks to grow to full size, and larger hydroponics systems will need more fish to supply adequate nutrients. A good rule to follow is to size your tank so that there are 10 gallons of water for every pound of fish at maturity or market size3. These numbers may change as the grower gains more experience with their selected fish species. A large tank will provide enough room for the fish while also helping to maintain proper water quality by diluting the fish waste in the water. Multiple tanks may be connected in larger systems to provide adequate space for the fish (Figure 3).
Fish culture tank size will depend on several factors. The size of your hydroponics setup and the amount of nutrients needed for it, and the number, type, and adult size of fish being grown all need to be considered before purchasing a tank. Various sizes and age groups of fish are grown together to help balance nutrient production and consumption, and the size and number of tanks should be configured accordingly. Common fish used in aquaponics are tilapia (Oreochromis spp.) and koi (Cyprinus spp.)1,2,4. In addition to the aquaponics system configuration when deciding which fish to grow, market research into consumer preferences and potential profits and costs should be considered when determining whether to grow food or ornamental species of fish.
Shape is an important factor to consider when picking out a fish culture tank. Circular, oval, or multisided tanks are the best options because they allow for improved water circulation and flow (Figure 3). Better movement improves water quality and the well-being of the fish. A circular tank and water flow also allow the fish to swim against the current created by the system's pump, which is part of the natural behavior of many fish. Maintaining the health of the fish is important, whether it's to have a high-quality product for sale or to humanely treat animals that might be living most of their lives in the tanks. If using a square or rectangular shaped tank, pick one that has rounded edges to improve water circulation and flow as well as fish well-being. Aeration of the water in the tanks is very important for fish health. This is accomplished through airstones and stirring of the water to add oxygen. Oxygen levels in the water should be kept as close as possible to 7–8 parts per million.
A circular, oval, or multisided tank is preferred to also aid in solids removal from the tank. In a tank with round sides, there are no spots where flow slows for solid materials (for example, feces, food, and other debris) to accumulate. The bottom of the tank can be funnel-shaped to help collect solids in the center for easier cleaning of the tank. A drain can also be placed on the bottom of the tank, in the center, to help with removal of solids during tank cleaning.
Covering the tanks is important for several reasons. Covers or netting made of waterproof materials will keep the fish in the tank, however the covering should not completely seal the tank because air exchange is important for fish respiration and maintaining water quality. An opaque cover will also reduce algae growth and build up, which can impact water quality and clog the circulation system. However, the opaque cover should not hinder the ability of the fish to see their food.
Water is pumped from the culture tank(s) to one or multiple tank(s) to filter the water. The first filter removes solid waste through settling or physical filtration. It is important to remove the solids before they enter the biofilter to avoid clogging. The second filter is the biological filter or biofilter. The flowing water also provides aeration to help improve water quality by removing the dissolved carbon dioxide produced by the fish and bacteria. This aeration also increases the oxygen level in the water for the plant roots and the fish to utilize.
There are many ways in which solids can physically be filtered out of the wastewater, including the use of inexpensive filter pads, fluidized sand, or bead filters, as well as higher-cost drum filters. The ideal type of filter will depend on the size of your system and operation. A three to one (3:1) fish culture tank volume to biological filter volume is usually adequate for most aquaculture operations5. Smaller systems may be fine with filter pads that will require frequent cleaning, but larger systems with larger numbers of fish may need to use mechanical filters that perform the cleaning automatically.
A biological filter provides a favorable environment for the beneficial bacteria to convert the ammonia that is excreted by the fish into nitrite, then, converted to nitrate nitrogen, which is much less toxic to fish than either ammonia or nitrite, and easily absorbed by the plant roots. This is accomplished by providing a substrate, such as sand, clay beads, plastic floating beads, Kaldeness beads, orchard netting, or shredded PVC ribbons, on which the beneficial bacteria grow. Cleaning and aeration of the biofilter is important to avoid it going anaerobic, a process that occurs when denitrifying bacteria will convert nitrate to nitrogen gas that is lost from the system. A biological filter can also include aquatic organisms, such as shrimp and snails, that will consume parts of the waste and convert them into nutrients that can be used by the plants.
Prior to use in the hydroponics portion of the operation, the filtered water is pumped to a settling tank to remove any particles that may not have been filtered. The settling tank is like a biofilter in that it contains a substrate upon which bacteria can grow. It may also incorporate organisms, like red worms, to treat the water. The settling tank filters particles by slowing down water flow, which allows solids to settle to the bottom of the tank. The organisms in the settling tank can use these settled solids for food and process them even further than the filtration system. In addition, the settling tank can be used as a planting medium to provide more area to grow crops for market. Planting in the settling tank adds challenges such as clogging of the media as solids are trapped in the plants' roots, increasing the frequency of cleaning the tank, and increasing the potential of damaging the plants during cleaning. Sizing of your settling tank will depend on the size of your aquaponics system and the amount of water that requires treatment.
As with other components in an aquaponics system, the methods of maintaining plants in water are varied and will depend on the goals and configuration of your operation. The planting systems available include rafts/floats, the nutrient film technique (NFT), and media-filled beds (geoponics). Rafts and floats are made of solid materials that float on the water surface and have holes in which to insert plants to allow their roots to reach the water and absorb nutrients (Figure 4). Nutrient-rich water from the settling tank can run continuously or intermittently (ebb and flow) through the system, either by being pumped or through a gravity-fed pipe network. Prefabricated systems can be purchased, but Styrofoam™ sheets can be used and configured with any number of holes to maximize the number and diversity of plants grown for market. The material chosen for the rafts/floats should not leach chemicals into the water.
With NFT, plants grow in long channels where a thin film of water flows down each channel, providing the plant roots with water and nutrients. As with the raft system, water flows from the fish tank, through filtration components, to the NFT channels where the plants are grown, and then back to the fish tank. With NFT, additional biological filtration is required because there is no large volume of water for beneficial bacteria to live and continue to convert the waste into usable nutrients for the plants.
A media-filled bed system (geoponics) uses containers (pots, bags, troughs, etc.) filled with gravel, perlite, or another soilless media for the planting bed. This bed is periodically drenched with nutrient solution from the fish tank and the water then drains back to the fish tank. This method is simpler to operate because it uses the fewest components and it does not have a filtration component in the aquaculture side of the system. However, these types of systems can be prone to clogging from excess solids in the water. The media-filled bed can be a good alternative for larger plants like tomatoes, peppers, and cucumbers that benefit from the nutrient and water-buffering capacity of the media, i.e., the media will retain some moisture and nutrients longer than bare-rooted NFT systems should the water circulation pump stop working. One issue to be mindful of in these systems is the potential for the wastewater to contact edible portions of the produce. Because of this, leafy greens may not be appropriate to grow in geoponics systems.
Water quality in the planting system is critical to the success of an aquaponics operation. Parameters such as dissolved oxygen, nitrogen in its various forms, water temperature, pH, and electrical conductivity are important to monitor and maintain at levels that will benefit both the plants and fish growing in the system.
What are the Benefits of Aquaponics Systems?
Self-contained aquaponics systems have several advantages:
What are Some Challenges of Aquaponics Systems?
Aquaponics systems for crop production have some challenges:
Aquaponics is a unique, alternative, and sustainable crop production system that utilizes no soil, uses water very efficiently, and can be built almost anywhere, including highly developed and densely populated urban communities that would be prohibitive to traditional agriculture. However, as a combination of two growing systems (aquaculture and hydroponics), it also brings with it many challenges related to system design, maintaining water quality, and crop selection. Planning an aquaponics system needs to take both benefits and challenges into consideration before starting such a venture.
There are many online resources available to those who are interested in aquaponics and diving deeper into these types of systems. While many of these resources separately cover either the aquaculture or the hydroponics components of aquaponics, they are still valuable as additional sources of information. Rutgers University resources (indicated with Rutgers, NJAES) can be counted on to provide reliable and verified information that is specific to the New Jersey agricultural community. In many cases, these Rutgers resources should be the first stop for gathering knowledge.
- Love, D.C., J.P. Fry, L. Genello, E.S. Hill, J.A. Frederick, X. Li, and K. Semmens. 2014. An International Survey of Aquaponics Practitioners. PLOS One. 9(7):1-10.
- Love, D.C., J.P. Fry, X. Li, E.S. Hill, L. Genello, K. Semmens, and R.E. Thompson. 2015. Commercial Aquaponics Production and Profitability: Findings from an International Survey. Aquaculture. 435:67-74.
- Mullins, C., B. Nerrie, and T.D. Sink. 2015. Principles of Small-Scale Aquaponics. Southern Regional Aquaculture Center (SRAC) Publication No. 5007. 8 p.
- Buttner, J., G. Flimlin, and D. Weber. 2008. Freshwater Aquaculture Species for the Northeast. Northeast Regional Aquaculture Center (NRAC) Publication No. 102-2008. 7 p.
- McGee, M. and C. Cichra. 2000. Principles of Water Recirculation and Filtration in Aquaculture. University of Florida Extension, Institute of Food and Agricultural Sciences Publication No. FA12. 4 p.
- AlShrouf, A. 2017. Hydroponics, Aeroponic and Aquaponic as Compared with Conventional Farming. American Scientific Journal for Engineering, Technology, and Sciences. 27(1):247-255.
- Okemwa, E. 2015. Effectiveness of Aquaponic and Hydroponic Gardening to Traditional Gardening. International Journal of Scientific Research and Innovative Technology. 2(12):21-52.
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