Aquaponics:
Combining Fish Farming and Hydroponics for Sustainable Food Production

Aquaponics is an innovative food production system that combines aquaculture (farming aquatic organisms) with hydroponics (growing plants without soil). This method creates a closed-loop ecosystem where fish waste serves as natural fertilizer for plants, and the plants purify the water, returning it to the fish tanks. With a growing global population, climate change, and depleting natural resources, aquaponics offers a promising path to creating sustainable food systems.

Historical roots and development of technology

The concept of integrating fish farming with crop production has ancient roots. Various civilizations have used similar methods for centuries, although modern aquaponics differs significantly from its predecessors. The Aztecs created floating gardens known as chinampas, where plants grew on rafts over organically enriched water. Asian farmers traditionally grew rice in flooded fields, where they also raised fish.

The scientific foundations of modern aquaponics were laid in the 1970s and 1980s. Professor Mark McMurty and Douglas Sanders of the University of North Carolina created the first successful closed-loop aquaponics system in the mid-1980s. In their setup, wastewater from fish tanks was used for drip irrigation of tomatoes and cucumbers grown in sand beds, which also functioned as biofilters. The purified water was then returned to the fish, completing the cycle.

The first large-scale commercial aquaponics operation, Bioshelters, was founded in Amherst, Massachusetts, in the mid-1980s and remains in operation today. In the early 1990s, farmers Tom and Paula Speraneo introduced the "Bioponics" concept, growing herbs and vegetables in gravel beds with an ebb and flow system, irrigated with nutrient-rich water from a 5,000-gallon tilapia tank. In the early 21st century, aquaponics gained particular popularity in Australia and Canada. Modern systems can be installed in vertical configurations, making them suitable for vertical farming and urban agriculture.

Biological Basics: The Nitrogen Cycle and the Role of Bacteria

The nitrogen cycle — a biochemical process that converts toxic nitrogen compounds into forms that are readily available for plant uptake — is at the core of an aquaponic system. Fish excrete ammonia (NH₃) as a primary product of protein metabolism through their gills and feces. High concentrations of ammonia are toxic to fish, causing stress, tissue damage, and even death.

Nitrifying bacteria play a central role in the conversion of ammonia. The nitrification process occurs in two stages. In the first stage, bacteria of the genus Nitrosomonas oxidize ammonia to nitrites (NO₂⁻). Nitrites are also toxic, although to a lesser extent than ammonia. In the second stage, bacteria of the genus Nitrobacter convert nitrites to nitrates (NO₃⁻). Nitrates serve as the main source of nitrogen for plants and are relatively safe for fish at moderate concentrations.

These bacteria colonize various surfaces in the system: the substrate in the beds (expanded clay, gravel, bioballs), plant roots, and the walls of the reservoirs. In systems with floating platforms (DWC) and nutrient film technology (NFT), the installation of external biofilters is required to provide sufficient surface area for bacterial colony growth. Biofilter maturation — the process of establishing a stable population of nitrifying bacteria — can take from several weeks to two months, depending on conditions.

Temperature, pH, and dissolved oxygen concentration significantly influence the activity of nitrifying bacteria. The optimal temperature for nitrification is 25-30°C, although the process can occur in a range of 5 to 35°C. pH values between 7 and 8 are considered optimal for bacterial activity. Nitrifying bacteria are aerobic organisms, so they require constant access to oxygen.

Components of an aquaponic system

All aquaponic systems contain several common elements that ensure the functioning of an integrated ecosystem.

Fish tanks

The fish tank is the starting point of the system. Its volume should be appropriate for the species and number of fish being raised, providing sufficient space for swimming and growth. Typical stocking densities range from 10 to 20 kg of fish per 1,000 liters of water, although this varies depending on the fish species, filtration efficiency, and aeration. The tank’s shape influences water circulation and solid waste removal — round or conical tanks provide better circulation than rectangular ones.

Mechanical filters

Mechanical filters remove solid particles — uneaten feed, fish waste — from the water before it enters the biofilter or plants. This prevents clogging of the system and improves the efficiency of biological filtration. Mechanical filters can be settling tanks, drum filters, cartridge filters, or simple mesh filters.

Biofilters

Biofilters provide a colonization environment for nitrifying bacteria. In systems with substrate-filled beds, the beds themselves act as the biofilter. In NFT and DWC systems, separate biofilters are required. The biofilter material must have a large surface area and good permeability to water and oxygen. Synthetic polymer materials, bioballs, ceramic rings, and crushed stone are used as biofilter fillers.

Hydroponic beds

The hydroponic components of the system provide space for plant growth. Plants can be grown in beds filled with substrate, on floating platforms, or in pipes and channels. The choice of method depends on the type of plants being grown, the scale of the system, and the available resources.

Pumps and aeration system

Water pumps circulate water between the system components. Pump capacity must ensure complete water circulation within the system several times per hour. The aeration system supplies oxygen to the fish and bacteria in the biofilter. Dissolved oxygen concentrations must be maintained at a minimum of 6 mg/L for optimal system operation.

Types of aquaponic systems

There are three main types of aquaponic systems, each differing in the method by which plants are grown.

Systems with beds on a substrate

Media-Based or Flood and Drain systems are considered the most common and easiest for beginners. Plants are planted in beds filled with expanded clay, gravel, perlite, or other inert material. Water from the fish tank periodically floods the beds and then drains back out.

The flooding and draining cycle ensures roots have access to water, nutrients, and oxygen. The substrate serves as both a mechanical and biological filter, trapping solid particles and providing a surface for bacterial growth. A bell siphon — a device that creates a siphon effect when a certain water level is reached — is often used for automatic drainage.

These systems are suitable for a wide range of plants, including leafy vegetables, herbs, and some fruiting crops. They are relatively easy to maintain and forgiving of minor errors. The downside is the need to regularly clean the substrate of accumulated solid waste.

Deep water culture systems

Deep Water Culture (DWC) systems, or floating platforms, are widely used in commercial aquaponics due to their ease of scalability. Plants are placed in mesh pots on floating foam or polystyrene platforms that float on the water’s surface. The plant roots hang freely in water typically 20-30 cm deep.

Nutrient-enriched water from the fish tanks continuously circulates through channels or planted tanks. Intensive aeration of the water is essential — without sufficient oxygen, roots can rot. DWC systems require separate mechanical and biological filters, as the beds themselves do not provide filtration.

This type of system is particularly suitable for growing leafy vegetables such as lettuce, Swiss chard, kale, and spinach. Plants in a DWC often experience rapid growth thanks to constant access to water and nutrients. Commercial growers value these systems for their space efficiency and ease of harvesting.

Nutrient layer technology systems

The Nutrient Film Technique (NFT) involves a thin film of water flowing through inclined channels or pipes. Plants are placed in mesh pots with a small amount of growing medium (expanded clay or gravel) in the channel openings. The plant roots are partially submerged in the moving water layer and partially suspended in the air, directly receiving oxygen.

Water flows by gravity through channels from a higher point to a lower point, where it is collected and returned to the system by a pump. NFT systems require less water than other types of systems. NFT systems require separate biofilters and mechanical filters.

NFT is suitable for plants with small, shallow root systems, such as lettuce, herbs, and spinach. Larger plants with extensive root systems can block water flow in the channels. NFT systems are popular in both home and commercial settings due to their efficient use of water and space.

Fish species for aquaponic systems

The choice of fish species depends on climatic conditions, feed availability, market demand, and compatibility with system parameters.

Tilapia

Tilapia is the most popular choice for aquaponic systems. These warm-water fish thrive at temperatures of 25-30°C. Tilapia exhibits rapid growth, high feed conversion, and disease resistance. They tolerate a wide range of water conditions, including fluctuations in pH and dissolved oxygen.

Tilapia produces a significant amount of waste, which ensures a good supply of nutrients for plants. Nile tilapia (Oreochromis niloticus) and Mozambique tilapia (Oreochromis mossambicus) are often used in aquaponics. Feed rates for tilapia in aquaponic systems range from 20.3 to 81.6 grams of feed per square meter of growing area per day.

Trout

Trout prefer cold water with temperatures of 14-16°C. Rainbow trout (Oncorhynchus mykiss) are the most commonly raised coldwater species in aquaponics. They require high water quality, good aeration, and cool temperatures. These fish are suitable for cooler climates or systems with temperature control.

Trout has excellent flavor and a tender flesh texture. The fish reaches a weight of 1,000 g in 14-16 months. Trout exhibit good disease resistance when maintained in adequate water quality. Wastewater from trout farming is successfully used to produce leafy vegetables in decoupled aquaponic systems.

Catfish

Various catfish species are used in aquaponics, including the channel catfish (Ictalurus punctatus) and the African catfish (Clarias gariepinus). Catfish are warmth-loving fish, growing optimally at temperatures of 24-29°C (75-85°F). They tolerate a variety of water conditions, including low dissolved oxygen levels.

Catfish demonstrate good growth and feed conversion. Fish production in an aquaponic system was 29% more efficient than in a recirculating aquaculture system and 75% more efficient than in a static system. The feed intake for catfish is 20-25 grams of feed per square meter of growing area per day.

Other species

Carp (Cyprinus carpio) is widely used in aquaponics, especially in Europe and Asia. Carp tolerate a wide range of temperatures and are easy to maintain. Feed consumption for carp ranges from 4.4 to 16.9 grams per square meter per day.

Ornamental fish such as koi and guppies are also used in aquaponic systems, particularly in educational and ornamental settings. Perch and eel have shown promising results in experimental systems. Species selection should take into account local climatic conditions, legal restrictions, and market demand for the end product.

Plants in aquaponic systems

Aquaponic systems support the cultivation of a wide range of plants with different nutrient requirements.

Leafy vegetables

Leafy greens are particularly well-suited for aquaponics due to their low nutrient requirements and rapid growth. Lettuce (Lactuca sativa) is the most recommended plant for beginners. Various varieties of lettuce — romaine, batavia, and iceberg — are successfully grown in all types of aquaponic systems. Lettuce has a short growing cycle (30-45 days), allowing for frequent harvests.

Spinach (Spinacia oleracea) prefers cool temperatures and high nitrogen levels. Kale (Brassica oleracea) is a hardy, nutrient-rich plant suitable for year-round cultivation. Swiss chard grows well on floating platforms and in raised beds with substrate. Leafy greens demonstrate excellent productivity in aquaponic systems, often comparable to or superior to hydroponics with proper nutrient management.

Herbs

Herbs are highly valuable for commercial aquaponics operations due to their market price and relative ease of cultivation. Basil (Ocimum basilicum) is one of the most popular plants in aquaponics. Genovese basil is the most commonly used, although Italian basil and purple basil are also grown. About 38.7% of basil cultivation studies used DWC systems, 31.1% used substrate-filled beds, and 17.9% used NFT.

Mint (Mentha spp.) has low water requirements and can be grown in small spaces. Parsley, cilantro (Coriandrum sativum), and oregano adapt well to aquaponic conditions. Herbs often require minimal nutrient additions, reducing system management costs.

Fruit-bearing crops

Tomatoes (Solanum lycopersicum) are popular in aquaponics, although they require more nutrients than leafy vegetables. They require good aeration and adequate phosphorus and potassium. Tomato-based systems maintain more stable water quality parameters and have lower electrical conductivity due to efficient nutrient removal. Commercial tomato yields in aquaponics can be comparable to those in hydroponics with proper nutrient management.

Peppers (Capsicum spp.) thrive in warm conditions and require a balanced supply of nutrients. Cucumbers are successfully grown in aquaponic systems with substrate-based beds. Strawberries show promising results in well-balanced systems.

Plant nutrient requirements

Nutrients derived from fish food may not provide sufficient levels of all elements for optimal plant growth. Iron, calcium, potassium, and phosphorus are often deficient in aquaponic water compared to hydroponic solutions. Adding micronutrients and iron improves the growth of mint and mushroom grass. Adding macronutrients (phosphorus and potassium) significantly accelerates lettuce growth, allowing it to exceed the performance of hydroponics.

Aquaponic water contains nearly six times more sodium than hydroponic solutions, resulting in three times higher sodium concentrations in edible plant parts. Marketable yields of basil and lettuce in basic aquaponic systems without additives were reduced by 56% and 67%, respectively, compared to hydroponics. Supplementing the aquaponic solution with mineral elements to commercial hydroponic levels significantly increases yields.

Water quality parameters

Monitoring and controlling water quality parameters is critical to the successful operation of aquaponic systems.

Temperature

Water temperature affects fish metabolism, bacterial activity, and plant growth. Most aquaponic systems operate in a range of 18-30°C. Warm-water species (tilapia, catfish) require temperatures of 25-30°C, while cold-water species (trout) prefer 14-18°C. Nitrifying bacteria are most active at 25-30°C. Temperature fluctuations should be minimized, as sudden changes create stress for fish.

Hydrogen index (pH)

The pH value represents the acidity or alkalinity of water. Aquaponic systems require a balance between the optimal pH for fish (6.5-8.5), plants (5.5-6.5), and bacteria (7-8). A compromise pH range of 6.0-7.0 is generally acceptable for all system components. Systems with floating platforms maintain a pH in the 6-8 range. Regular pH monitoring is necessary because the nitrification process produces acid, gradually lowering the pH.

Dissolved oxygen

Dissolved oxygen concentrations must be maintained at a minimum of 6 mg/L for optimal aquaponics performance. Oxygen is essential for fish respiration, plants for nutrient uptake, and bacteria for nitrification. Oxygen levels decrease with increasing temperature, increased fish biomass, and the accumulation of organic matter. NFT systems maintained higher dissolved oxygen levels (5.8 ± 0.6 mg/L) compared to substrate-based systems.

Nitrogen compounds

Ammonia concentrations should be maintained below 1 mg/L, preferably close to zero. Nitrite levels should also be minimal, below 1 mg/L. Nitrate is the end product of nitrification and the primary source of nitrogen for plants. Nitrate concentrations typically range from 5 to 150 mg/L, depending on fish stocking density and plant removal efficiency. Regular testing of these parameters is essential for early detection of system problems.

Other parameters

Electrical conductivity (EC) and total dissolved solids (TDS) indicate the concentration of dissolved minerals in water. Tomato and basil-based systems had lower EC due to more efficient nutrient removal. Total alkalinity and water hardness affect the system’s buffering capacity — its ability to withstand changes in pH. Turbidity indicates the presence of suspended solids. Systems should maintain turbidity below 10 NTU.

Advantages of aquaponic systems

Aquaponics offers numerous advantages over traditional farming methods and separate aquaculture or hydroponics systems.

Water efficiency

Aquaponics uses up to 90% less water than traditional soil farming. Water is continuously recirculated within the system, with losses occurring only through plant transpiration and evaporation. This makes aquaponics particularly valuable for regions with limited water resources. The closed-loop nature of the system prevents water pollution from aquaculture wastewater.

Efficient use of space

Aquaponic systems can be installed vertically, enabling high-density production in a limited space. Vertical farming can use 28 times less land than traditional farming. The systems are suitable for urban areas, rooftops, greenhouses, and indoor spaces. Simultaneous production of fish and plants in the same space increases the overall productivity of the system.

Sustainability and eco-friendliness

Aquaponics minimizes the use of synthetic fertilizers and pesticides. Fish waste serves as a natural source of nutrients, eliminating the need for mineral fertilizers. The integrated nature of the system reduces greenhouse gas emissions compared to traditional production. Decoupled aquaponic systems demonstrate significant reductions in greenhouse gas emissions due to savings in inorganic fertilizers.

Productivity

Plants in aquaponic systems often grow faster than in traditional soil gardens due to the constant availability of nutrients and optimal growing conditions. The systems allow for year-round production under controlled conditions. The simultaneous production of animal protein (fish) and plant-based products diversifies income sources.

Local food production

Aquaponics enables localized production of fresh produce year-round. This reduces transportation costs, emissions, and dependence on remote suppliers. Urban aquaponics can improve food security for urban populations. These systems provide access to fresh vegetables and fish in regions with unfavorable climates or limited agricultural land.

Challenges and Limitations

Despite its many advantages, aquaponics faces a number of technical, economic and practical limitations.

Initial investment

Setting up an aquaponic system requires a moderately high initial investment. This includes tanks, pumps, piping, aeration systems, biofilters, and plant growing structures. Small home systems can be relatively affordable, but commercial installations require significant financial resources. Economic barriers, such as operating costs and energy-intensive components, hinder the viability of small-scale aquaponics.

Energy consumption

Aquaponic systems require a constant power supply to operate pumps, aerators, temperature control systems, and lighting. Energy costs, especially for artificial lighting in closed systems, represent a significant portion of operating expenses. Power outages can quickly lead to fish deaths due to lack of oxygen. Using renewable energy sources can reduce both the carbon footprint and operating costs.

Difficulty of management

Aquaponic systems require an understanding of water chemistry, fish physiology, plant needs, and microbiology. Balancing the needs of fish, plants, and bacteria requires constant monitoring and adjustment. A lack of professional knowledge of water chemistry and system maintenance creates difficulties for practitioners. Selecting appropriate fish and plant species and determining optimal stocking densities are crucial.

Disease management

Treating fish diseases in aquaponic systems is complicated by the presence of plants and beneficial bacteria. Many medications used in traditional aquaculture are toxic to plants or impair the function of nitrifying bacteria. Disease prevention through maintaining optimal water quality, proper feeding, and quarantining new fish is the preferred strategy. Plant diseases also require careful handling due to their potential impact on fish.

Nutrient availability

Fish feed nutrients may not provide all the necessary elements in optimal amounts for all plants. Iron, calcium, potassium, and phosphorus deficiencies are common in basic aquaponic systems. Supplementing with nutrients may be necessary for high-yielding fruiting crops, but this increases complexity and costs. Decoupled systems, where the fish and plant cycles are partially separated, offer greater flexibility in nutrient management.

Commercial application and market development

Aquaponics is gradually moving from experimental and home-based systems to commercial operations.

Market size and growth

The global aquaponics market was valued at US$1,250 million in 2025. The market is projected to grow to US$1,370 million in 2026 and to US$2,910 million by 2034. The growth is driven by increased awareness of food security, the need for sustainable production methods, and urbanization.

Commercial operations

Commercial aquaponics farms are expanding worldwide, particularly in developed countries with high population densities and limited agricultural land. Floating platform systems are the most popular in commercial aquaponics due to their ease of scalability and high productivity. Vertical aquaponics systems are being integrated into urban infrastructure, including building rooftops, parking structures, and specialized vertical farms.

Application in education

Aquaponics is recognized as an effective teaching tool, demonstrating biological cycles, ecological relationships, and sustainable agriculture. School aquaponics systems serve as a platform for integrating STEM education and problem-based learning. The systems raise students’ awareness of the climate crisis and the need for alternative food sources.

Application in developing countries

Aquaponics offers a potential solution to food security in developing countries. These systems can produce nutritious food in small spaces with minimal water use. Rural communities face challenges such as declining agricultural productivity, poor soil fertility, and limited access to modern technology. Aquaponics allows communities to grow food using minimal land and water resources. Building communities for knowledge sharing is vital for the continuous improvement of small-scale aquaponics.

Technological integration

The integration of Internet of Things (IoT) technologies into aquaponics enables automation and real-time monitoring of system parameters. Sensors monitor pH, temperature, water level, turbidity, and dissolved oxygen. Data is visualized through mobile apps, providing continuous monitoring, second-by-second updates, and automated notifications when thresholds are exceeded. The use of artificial intelligence and automation signals the maturity phase, where sensors and automated control systems precisely adjust water quality, lighting, and nutrient delivery to optimize growing conditions.

Decoupled aquaponic systems

Decoupled aquaponic systems (DAPS) represent an evolution of traditional aquaponics, where the fish and plant growing components are partially separated. In traditional systems, water is continuously circulated between the fish and plants. In decoupled systems, the cycles can be controlled independently, providing greater flexibility in optimizing conditions for each component.

Decouple systems have the potential to become some of the most efficient sustainable production systems for the combined production of animal protein and plant crops. Recirculating aquaculture systems for fish production are combined with hydroponics for soil-free plant growth, recycling dissolved nutrients derived from fish metabolism. Lettuce production using a conventional hydroponic nutrient solution was compared with decoupled aquaponics using nutrient-rich fish water.

Lettuce yield and quality were comparable between the systems, but decoupled aquaponics demonstrated a significant reduction in greenhouse gas emissions due to savings in inorganic fertilizers. The systems allow for independent regulation of pH, temperature, and nutrient concentrations for fish and plants. Aquaculture water yield depends on the evapotranspiration rate in the hydroponic component.

Features of seasonal dynamics

Seasonal factors such as temperature, UV intensity, and daylight hours can cause changes in water quality and plant nutrient status. Seasonal shifts impact system efficiency, crop physiology, nutrient uptake, and operating costs, even under controlled conditions.

Warm-season leafy vegetables and herbs, such as basil, amaranth, and mint, are more resilient in summer. Crops such as lettuce, kale, and parsley thrive in winter or in actively cooled conditions. Ornamental crops such as marigolds, nasturtiums, and lilies exhibit distinct seasonal windows of productivity based on temperature and photoperiod.

The concentrations of moisture, ash, fiber, carbohydrates, and protein in red chili peppers, red tomatoes, green spinach, and lettuce from an aquaponic farm showed significant differences between seasons. Levels of antioxidant activity, total phenolic content, and flavonoids also varied depending on the season. The lack of standardized growing schedules adapted to agroclimatic zones hinders the optimization of seasonal production.

Microbiome of aquaponic systems

Bacterial and fungal communities in aquaponic systems extend beyond nitrifying bacteria. The microbiome includes diverse groups of organisms colonizing biofilters, plant roots, and nutrient solution. An ecological study of the bacterial microbiome in an aquaponic system during the lettuce growth cycle revealed stability in the predominant taxa (Luteolibacter, Flavobacterium, and Nitrospira) in the biofilter.

The results provide evidence of similarities between the root communities of lettuce grown in aquaponics and soil (Gammaproteobacteria, Flavobacterium, Pseudomonadaceae, Sphingomonadaceae). This demonstrates that aquaponics may be similar to soil production in terms of microbial life. The composition of the bacterial and fungal communities varies in different habitats: leaves, roots, substrate, and nutrient solution.

Factors such as system type, plant age, nutrient solution parameters (pH, conductivity, temperature), and environmental conditions (humidity) significantly influence microbial community changes. The practice of continually transferring microbial communities from existing systems can enhance or hinder aquaponic productivity. Lettuce growth was significantly reduced in systems inoculated with bacteria from existing aquaponic systems compared to commercially obtained bacteria under nitrogen-limited conditions.

Integrated multitrophic systems

Integrated multitrophic aquaponics systems (IMTA aquaponics) represent a further development of this concept. These systems incorporate multiple trophic levels, where waste from one biological component serves as a nutrient source for another. IMTA systems can incorporate fish, shellfish, algae, and plants.

The study used a solar-powered system for two separate IMTA aquaponics systems using nutrient film technique (NFT) and floating platform technology (FRS). Using FRS and NFT as hydroponic systems increased the dietary efficiency of nitrogen and phosphorus to 83.51% N and 96.82% P, respectively. The IMTA aquaponics system, as a biointegrated food production system, can convert a large portion of fish feed waste into valuable products suitable for desert, rural, and urban areas in poor and developing countries.

A preliminary study examining the impact of mussel integration on water quality improvements in an aquaponic system demonstrated that the freshwater mussel Unio crassus can act as a biological filter to remove organic waste and purify water. Systems with substrate-based beds achieved significantly lower suspended solids concentrations (14.2 ± 2.1 mg/L), while NFT systems maintained higher dissolved oxygen levels (5.8 ± 0.6 mg/L) and supported greater plant growth.