Basics of aquaponics

The term aquaponics stands for a combination of aquaculture and hydroponics. It is typical that the combined cultures complement each other in the form of a circular economy. The fish culture serves as a nutrient producer, while the plants as consumers live on the waste products from the fish culture, which has been processed by bacteria.

This is the same process that takes place in inland waterways and that has been commonly described as the "nitrogen cycle". In contrast to conventional agriculture, which can only use a small section of the nutrient cycle, a complete biological cycle is mapped with aquaponics. In comparison with nature, this corresponds to a complete ecosystem, such as a lake: fish or other animals living in the water produce nutrients that are processed by bacteria and absorbed by plants.

Hydroponik-Salatkultur im vertikalen NFT-System
Lettuce culture in the vertical farming system


Aquaponics is not only sustainable in several ways. No, aquaponics is also the leap into a sustainable way of thinking in cycles.

Not only the water, but also the nutrients and the cultures are in a closed system. Nothing can be lost but everything has a purpose. Within this logic, we also use the other substances from culture that cannot be used by humans. 

The advantages of the closed system:
A small part of the water is lost only through evaporation and evapotranspiration (absorption by plants). All other nutrients are retained. This is positive in terms of phosphorus recovery and prevents nitrate entry into the groundwater. This makes aquaponics extremely resource-saving.

Furthermore, neither antibiotics nor pesticides (or insecticides, fungicides, etc.) can be used in aquaponics, as this would damage the other cultures in the cycle. Pests are constantly observed in aquaponics, but they are fought without chemical agents. This happens exclusively through beneficial insects, which in turn destroy the pests.

The Sustainable Development Goals

The United Nations has drawn up 17 goals for sustainable development, which are intended to secure sustainable development on an economic, social and ecological level worldwide. These “Sustainable Development Goals” (SDGs) came into force on June 1st, 2016 with a term of 15 years. Aquaponics already addresses 8 of these 17 sustainability goals.

Closed cycles replace raw and waste materials

The resource-saving properties of aquaponics are no coincidence, because the switch to a closed cycle economy also makes the leap to production without waste. 

A comparison of the two individual cultures, aquaculture and hydroponics, clearly shows why we do not have any waste materials in aquaponics and therefore no nutrients are wasted.

Losses in aquaculture: water and sludge

Loss in hydroponics: water and used nutrient solution

Losses in aquaponics: Very little water

Aquaponik und die Ziele für nachhaltige Entwicklung der Vereinten Nationen (SDG)
Goal 2: No hunger
Goal 8: Decent Work and Economic Growth
Goal 9: Industry, Innovation and Infrastructure
Goal 11: Sustainable cities and communities
Goal 12: Sustainable consumption and production
Goal 13: Climate protection measures
Goal 14: life under water
Goal 15: Life on Land

Types of application

Aquaponics can be very diverse, both in their size and in their characteristics. From the small and simple backyard area to several hectares in the modern greenhouse, everything is possible. 

Different types of systems

Analogous to the variety in horticulture, aquaponics can also be operated in all conceivable sizes, cold or warm, in film tunnels or greenhouses or even outdoors. Here are some examples of aquaponic facilities, with very different focuses. 

State of the art aquaponics with modern hydroponics

When talking about large-scale systems, this usually means aquaculture in combination with hydroponics in a greenhouse. They make it possible to create the optimal conditions for all cultures. As is usual in horticulture, the greenhouse sizes are hardly limited in size due to the modular structure. True to the rule in agriculture and horticulture, the following also applies here: the more area, the more harvest, the lower the production prices. Therefore aquaponics is even more worthwhile on an agricultural scale.

Aquaponics with biogas / CHP - electricity / heat generation for own use

From a size of around 15,000 square meters, it is worthwhile to use your own biogas plant. Together with a combined heat and power unit (CHP), the system can be completely supplied with heat and electricity. The biogas plant only uses secondary raw materials from the aquaponics plant and thus generates its own heat / electricity requirements. The comparatively small biogas plant is NOT (primarily) used to feed electricity into the power grid.

Passive Solar Greenhouse and thermal greenhouse optimization

Energy consumption plays an important role in aquaponic facilities. Since fossil fuels are not an option for sustainable projects, the energy concept is crucial. The heat and power requirements can be reduced to a minimum. The passive solar construction of the greenhouse with a thermal storage means that the night can be bridged and the season extended. 

Simple cold aquaponics systems or modules

In addition to complex greenhouse solutions, aquaponics can also be designed simply and require little energy and electricity. In a cold aquaponics facility, the cultures are matched to seasonal operation. With the cold, fish shut down their metabolism, there is less light available. The plant cultures are adapted accordingly (winter varieties). Aquaculture can also be greatly simplified and in many cases even reduced to just one feed pump, while all other modules only use gravity for the flow. 

Basilikum Topfkultur in Aquaponik-Großanlage
Aquaponics system, basil plant part
Basilikum Topfkultur in Aquaponik-Großanlage
with pot culture on ebb and flow tables

Cultures in aquaponics

In principle, soilless cultivation can be carried out using hydroponics with almost any plant culture. Whether fruit or leafy vegetables, herbs, fruits, in the end it is just a question of the cultivation method. However, the effort involved in greenhouse cultivation is by no means worthwhile for all crops. An investment cannot be refinanced with the proceeds of a potato, corn or beet crop. 

Hydroponic growing methods

1. Deep Water Culture (DWC)
For e.g. Salad, leafy vegetables such as spinach, Swiss chard, etc. herbs, various types of cabbage

2. Nutrient Film Technique (NFT)
Typical for e.g. Tomatoes, cucumbers, lettuce, leafy vegetables, can also be used universally as a vine system.

3. Grow beds, ebb / flow tables, pods, etc. Container with substrate (e.g. expanded clay, gravel)
For e.g. Zucchini, aubergine, chilli, paprika, all of which can be used universally (tomatoes, etc. are also possible, provided that Rankleitunt, etc. is available).


Aquaponics also offers maximum flexibility in relation to aquaculture. Almost all cold and Warm water fish are an option. Even seawater fish come into question, but then only together with algae or salt-tolerant plants. 

In principle, a lot is possible, but production facilities should generally be profitable. Therefore, the financial outlay must also be compared with the benefit and the achievable price on site on the market. 

Aquaponics concepts

The reasons for building an aquaponics facility can be very different. Depending on the initial situation and strategy, aquaponics can be considered for many business models. That is why we briefly outline the most frequently used strategies here.

1. State of the art aquaponics facility

The variant described above as a modern greenhouse, in which there is space for aquaculture, hydroponics, water treatment and, if necessary, other circuits. With thermal optimization 

Hydroponik-Teil in Aquaponik-Großanlage
Aquaponics system, plant part, tomatoes

2. Aquaponics as a supplement for biogas plants or agriculture

Due to several amendments to the Renewable Energy Sources Act (EEG), biogas plants require heating concepts. However, a school or a water park is not always nearby to make the most of the heat. Aquaponics systems can be designed precisely for the required heating concept.

3. Aquaponics for special crops (diversification for farmers)

 Aquaponics has many points of contact with agriculture. Therefore only examples can be given here. Cultures that are not necessarily the typical food fish are often worthwhile. Of course, aquaponics also works with ornamental fish. Invertebrates such as Crayfish available. These can achieve comparatively high sales prices on the market.

4. Aquaponics modules or supplementation of previous cultivation methods

Of course, it is also possible the other way around to add the cultures that are missing for aquaponics. This applies, for example, to horticulture, which is still dependent on nutrient solutions. Supplementing the consumer culture with producers in the food chain can also pay off in monetary terms.

Tilapia mariae, ein beliebter Aquaponik-Fisch
Common in aquaponics, Tilapia mariae


The development in aquaponics is currently advancing very quickly. Great advances have been made in science in recent years. But the profitability of aquaponics has also been researched in the meantime, which means that investments in large aquaponics systems are now less risky.

In order to use the synergies of aquaponics ecologically and economically, more and more such large-scale systems will emerge in the future, which will also cover market niches. They are already the solution to our ecological problems and are therefore not affected by the continuously increasing requirements for the ecological compatibility of agricultural and horticultural systems in the future. 

The graphic below comes from Chapter 15Smarthoods: Aquaponics Integrated Microgridsin the book "Aquaponics Food Production Systems" and shows the processes combined with one another.

Tilapia mariae, verbreiteter Fisch in der Aquaponik
Tilapia mariae

Conversion of nutrients

The processes in detail: 

  1. Pellet feed (depending on the type of fish, vegetarian or with animal protein, but without fish meal from the fishery) is consumed by the fish.
  2. End products of the fish metabolism are first converted into nitrite and then into nitrate by bacteria.
  3.  Plants take in nutrients from the water through their roots.