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Aquaponics

Aquaponics is a great example of sustainable agriculture. Aquaponics is defined as the integrated culture of aquatic animals and plants. This form of polyculture (growing more than one crop in the same environment) is becoming popular in recirculation aquaculture systems (RAS). Aquaponics naturally works because of the differing nutrients plants and animals require to survive. For example, plants use carbon dioxide for photosynthesis and produce oxygen as a waste product. Conversely, animals use oxygen during respiration and produce carbon dioxide as a waste product. This simple example explains one aspect of aquaponics but more detailed information is available below.

Aquaponics Bed

"Floating Bed" in an Aquaponics Greenhouse


The term "aquaponics" is derived from a combination of two words: "aquaculture" and "hydroponics". In Kentucky, many farmers are familiar with horitculture and hydroponic growing techniques. In aquaponics, the same soilless culture methods can be used. But instead of using a formulated liquid solution, aquaponics depends on the natural process of nitrification to deliver nitrates to plants.

The Process of Nitrification

  • Production of Ammonia
    The process of metabolism in animals requires food and produces waste products that are released from the body. Chemically, the major waste produced is ammonia. Fishes and other aquatic animals (with gills) release ammonia in three ways: (1) urine, (2) fecal material, and (3) directly from the gills as a dissolved gas. Ammonia is highly toxic to these animals and levels must be reduced in RAS waters. Nitrifying bacteria remove ammonia and nitrite but need oxygen to survive.

  • Nitrifying Bacteria (Biofilter)
    Nitritying bacteria consists of two genera of useful bacteria (i.e. Nitrosomonas and Nitrobacter). Such bacteria are naturally-occurring and responsible for reducing ammonia and nitrite levels in aquatic environments. Nitrosomonas feed on dissolved ammonia and produce another nitrogenous compound called nitrite as their waste product. Nitrite can also be toxic to aquatic animals but in much higher levels than ammonia. The second genera of nitrifying bacteria, Nitrobacter, feed on nitrite and produce nitrate as a waste product. Nitrate is less toxic to aquatic animals than nitrite. Plants use nitrates as fertilizer. In fact, terrestrial farmers have used aluminum nitrate as a liquid fertilizer for years. But through the process of nitrification, nitrates are naturally available for useful plant production (as opposed to unwanted algae).

Popular Aquaponic Culture Techniques

  • Nutrient Film Technnique (NFT)
    This area is used to house culture species. Popular tank shapes are either round or rectangular. However, the ideal tank shape depends on the aquatic species being cultured.

  • Floating Bed
    This area is used to house culture species. Popular tank shapes are either round or rectangular. However, the ideal tank shape depends on the aquatic species being cultured.

  • Ebb & Flow
    This area is used to house culture species. Popular tank shapes are either round or rectangular. However, the ideal tank shape depends on the aquatic species being cultured.

Return to Technical Information for Classroom Aquaculture Systems

 



 
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