Aquaponics is a word combined from “aquaculture” (the growing of fish and other aquatic animals) and “hydroponics” (the growing of plants without soil) in one recirculating environment.
This recirculating environment is a form of aquaculture in which the waste produced by fish or other water animals provides food for the water plants, and the plants keep the water clean.
Aquaponics is not new. In fact, it’s nearly as old as the paper, but not long ago it was recognized again as an alternative for sustainable development.
The earliest evidences of this circular environment are from Egypt. The ancient Egyptians used to take advantage of the periodic flooding of the Nile River to cultivate plants and fish simultaneously in flooded areas. Thus, they obtained better, larger, and healthier harvests.
In fact, the famous Hanging Gardens of Babylon were based on aquaponic techniques to ensure the fertilization of the plants that lined their walls.
They are not the only ones. The Aztecs also developed a unique system of agricultural cultivation through the construction of floating rafts or “chinampas.” They built them using trunks and sticks and covered them with soil, leaf litter, grass, fruit, and vegetable peels.
These “chinampas” were built on the lakes and lagoons of the central valleys of Mexico. In these areas, they cultivated various plant species, including flowers and vegetables, while collecting fish and sludge through canals. They later used these resources to fertilize the “chinampas” themselves.
Approaching the present
Even more widely known and practiced today is the case in Asia. In southern China and Thailand, for thousands of years, farming systems combined rice and fish production at the same time. Nowadays, many initiatives still exist in rural Asia, based on ancestral traditions, where farmers combine vegetable, fish, and livestock farming in different ways. These modalities are known as integrated agro-aquaculture and include aquaponics techniques.
Modern aquaponics would come from the hand of John and Nancy Todd, along with William Mc Larney, after the creation of the “New Alchemy” Institute in the U.S. in 1969. They carried out different research on organic agriculture and sustainable aquaculture and developed the design of “bio-shelters,” leading the next steps.
Basic components of aquaponics: fishes, nitrifying bacteria and plants
Aquaponics freshwater systems rely on three main components: freshwater aquatic animals (the fish), nitrifying bacteria, and plants. All three living entities depend on each other to survive, but depending on the combination it’s possible to achieve the maximum growth output or not.
- Fish. Their waste (fecal and urine) acts as a natural fertilizer for the plant with bacteria intervention.
- Bacteria. The system converts fish waste into nutrients that the plants subsequently absorb. The key issue in this is to maintain a healthy bacterial colony in the system. It can be present in the biofilter, grow beds, and fish tanks.
- Plants. They consumed the fish fertilized. They are planted in the grow bed, pipes, or floating rafts, and the recommendation is to avoid nutrient-hungry plants until the system is fully established.
Aquaponic systems vary in size, from small indoor units to large retail units, and can be freshwater systems or contain brackish or salt water.
One recirculating environment
There are three main types of systems…
Media-based/flood and drain system
It uses a growing bed or container filled with growing media (usually gravel, lava rock, or clay pebbles) to plant the crops. Water from the fish tank periodically inundates the container through a bell siphon. That gives the plants access to nutrients. The water is then returned to the fish tank, where a new cycle begins. As a result, all the waste is decomposed in the culture bed. In addition, sometimes worms are added to the growing medium to help break down all the waste.
NFT (Nutrient Film Technique)
Plants grow in long, narrow canals. A fine film of water flows continuously through each canal to feed the plant roots with water, nutrients, and oxygen. The water flows from the tank through the filtration components, passes along the NFT canals where the plants are grown, and returns to the tank, as in the pond. In NFT, a separate biofilter is necessary as there is insufficient surface area for beneficial bacteria to inhabit.
Nutrient-rich water flows through the long channels, usually at a depth of about 20 cm, while the rafts (made of polystyrene or foam sheets) float on top. Plants grow on the boards of the rafts, which support them inside holes using net pots. The roots of the plants hang in the oxygenated, nutrient-rich water, absorbing oxygen and nutrients to grow rapidly. The nutrient-filled water flows continuously from the fish tank through the filter process, then into the raft tank in which plants grow, and finally back into the fish tank. Most often, the raft is separate from the tank.
Thus, aquaponic systems are increasingly becoming a sustainable solution for plants and fish. This way of bringing together what land and water offer us is becoming popular and also adding homemade projects with zero waste philosophy.