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Aquaponics is an integrated aquaculture (growing fish) and hydroponic (growing soilless plants) system that mutually benefits both environments.  Aquaponics uses no chemicals, requires one tenth or 10% ofuaculturthe water needed for field plant production and only a fraction of the water that is used for fish culture (Aqe).

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The waste from fish tanks is treated with natural bacteria that converts the waste, largely ammonia, first to nitrite and then to nitrate. The fish waste absorbed by plants is pumped to a bio-filter system as a nutrient solution for the growing plants (Grow Bed). The only external input to the system is food for the fish. Both systems complement each other as a single unit, not as separate units.

Once the system is initialized the water stays Ph balanced and remains crystal clear. The water is recycled with a small amount of water added weekly to compensate for what is lost by evaporation and transpiration by the vegetables. Aquaponics is the future of home gardening and commercial fresh food production.

Greenhouse growers and farmers are taking note of Aquaponics for several reasons:

* Hydroponic growers view fish-manured irrigation water as a source of organic fertilizer that enables plants to grow well.

* Fish farmers view hydroponics as a bio-filtration method to facilitate intensive re-circulating aquaculture.

* Greenhouse growers view Aquaponics as a way to introduce organic hydroponic produce into the marketplace, since the only fertility input is fish feed and all of the nutrients pass through a biological process.

* Food-producing greenhouses – yielding two products from one production unit – are naturally appealing for niche marketing and green labeling.

* Aquaponics can enable the production of fresh vegetables and fish protein in arid regions and on water-limited farms, since it is a “water re-use” system.

* Aquaponics is a working model of sustainable food production wherein plant and animal agriculture are integrated and recycling of nutrients and water filtration are linked.

* In addition to commercial application, Aquaponics has become a popular training aid on integrated bio-systems with vocational agriculture programs and high school biology classes.

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The technology associated with Aquaponics is complex. It requires the ability to simultaneously manage the production and marketing of two different agricultural products. Until the 1980s, most attempts at integrated hydroponics and aquaculture had limited success. However, innovations since the 1980s have transformed Aquaponics technology into a viable system of food production. Modern Aquaponic systems can be highly successful, but they require intensive management and they have special considerations.

Nutrients in Aquaculture Effluent: Greenhouse growers normally control the delivery of precise quantities of mineral elements to hydroponic plants. However, in Aquaponics, nutrients are delivered via Aquacultural effluent. Fish effluent contains sufficient levels of ammonia, nitrate, nitrite, phosphorus, potassium, and other secondary and micronutrients to produce hydroponic plants. Naturally, some plant species are better adapted to this system than others. The technical literature on Aquaponics provides greater detail on hydroponic nutrient delivery; especially see papers cited in the Bibliography by James Rakocy, PhD.

Plants Adapted to Aquaponics: The selection of plant species adapted to hydroponic culture in Aquaponic greenhouses are related to stocking density of fish tanks and subsequent nutrient concentration of Aquacultural effluent. Lettuce, herbs, and specialty greens (spinach, chives, basil, and watercress) have low to medium nutritional requirements and are well adapted to Aquaponic systems. Plants yielding fruit (tomatoes, bell peppers, and cucumbers) have a higher nutritional demand and perform better in a heavily stocked, well established Aquaponic system. Greenhouse varieties of tomatoes are better adapted to low light, high humidity conditions in greenhouses than field varieties.

Fish Species: Several warm-water and cold-water fish species are adapted to re-circulating aquaculture systems, including tilapia, trout, perch, Arctic char, and bass. However, most commercial Aquaponic systems in North America are based on tilapia. Tilapia is a warm-water species that grows well in a re-circulating tank culture. Furthermore, tilapia is tolerant of fluctuating water conditions such as pH, temperature, oxygen, and dissolved solids. Tilapia produces a white-fleshed meat suitable to local and wholesale markets. The literature on tilapia contains extensive technical documentation and cultural procedures. Barramundi and Murray cod fish species are raised in re-circulating Aquaponic systems in Australia.

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Water Quality Characteristics: Fish raised in re-circulating tank culture require good water quality conditions. Water quality testing kits from Aquacultural supply companies are fundamental. Critical water quality parameters include dissolved oxygen, carbon dioxide, ammonia, nitrate, nitrite, pH, chlorine, and other characteristics. The stocking density of fish, growth rate of fish, feeding rate and volume, and related environmental fluctuations can elicit rapid changes in water quality; constant and vigilant water quality monitoring is essential.

Biofiltration and Suspended Solids: Aquaculture effluent contains nutrients, dissolved solids, and waste byproducts. Some Aquaponics systems are designed with intermediate filters and cartridges to collect suspended solids in fish effluent, and to facilitate conversion of ammonia and other waste products to forms more available to plants prior to delivery to hydroponic vegetable beds. Other systems deliver fish effluent directly to gravel-cultured hydroponic vegetable beds. The gravel functions as a “fluidized bed bioreactor,” removing dissolved solids and providing habitat for nitrifying bacteria involved in nutrient conversions.

Component Ratio: Matching the volume of fish tank water to volume of hydroponic media is known as component ratio. Early Aquaponics systems were based on a ratio of 1:1, but 1:2 is now common and tank: bed ratios as high as 1:4 are employed. The variation in range depends on type of hydroponic system (gravel vs. raft), fish species, fish density, feeding rate, plant species, etc. Further, when shallow bed systems only three inches in depth are employed for the production of specialty greens such as lettuce and basil, the square footage of grow space will increase four times. Depending on the system design, the component ratio can favor greater outputs of either hydroponic produce or fish protein. A “node” is a configuration that links one fish tank to a certain number of hydroponic beds. Thus, one greenhouse may contain a multiple number of fish tanks and associated growing beds, each arranged in a separate node.

 

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