Aquaponics

IMG_4504Aquaponics is a sustainable food production system. It is a polyculture that merges conventional fish-farm aquaculture (tank-raised animals such as fish, prawns, crayfish or snails) with hydroponics (plants grown in water) in a cooperative, mutually beneficial relationship.

 

This symbiosis works as follows: the waste matter from the aquaculture accumulates in the water. The ammonia in the excrement increases toxicity for the fish. This water is then led off to the hydroponic system where the waste matter is broken down by bacteria, then filtered out by the plants as nutrients. The cleansed water is then recirculated back to the fish. The nutrients contained in the fish feces are reused to nourish the crop plants, and the crop plants re-purify the water for the fish.

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This system is very self-sustaining and cost efficient. The fish can be raised to be eaten and the plants harvested and eaten. The aquaponic system can be of any size and complexity, and the types of food grown can vary as much as any type of symbiotic farming discipline allows.

The types of plants that work best in this system are green leaf vegetables such as Chinese cabbage and lettuce, but other very profitable vegetation is basil, roses, tomatoes, okra, cantaloupe, and bell aquaponic_smallpeppers. Beans, peas, watercress, radishes, strawberries, onions, turnips, parsnips, sweet potato, and other herbs also grow well in this environment.

For the aquacultural element, freshwater fish are the most common aquatic animal raised in this method. Tilapia is the most popular fish to be raised in home-based edible aquaponic systems, but barramundi, Silver Perch, catfish, Jade perch and Murray cod are also used. In a non-edible fish-farm, koi and goldfish can also be used.

 

The bacterial culture of this system is of great importance. A bacterial colony will usually reside on all solid surfaces throughout the system that are in contact with the water. These bacterial colonies are what regulate the full assimilation of ammonia and nitrite. For this reason, most aquaponics systems have a biofiltering unit to help facilitate the growth of these bacteria. During startup, ammonia level spikes typically occur. Nitrite levels peak later on. After a system has been stabilized, ammonia levels and nitrite levels are in equilibrium. Because the nitrification process acidifies the water, non-sodium bases such as potassium hydroxide or calcium hydroxide can be added to neutralize the water’s pH levels. This prevents too much acidification.

The best way to deal with solids buildup is through the use of worms, which digest and liquefy the waste matter from the fish to be better absorbed and utilized by the plants.

PicoSystemJackRose1Typical build ratios are 0.5-1 square foot of grow space for every 1 US gallon (3.8 L) of aquaculture water in the system. 1 US gallon (3.8 L) of water can support between 0.5 lb (0.23 kg) and 1 lb (0.45 kg) of fish stock. Not only is the aquaponic system self-sustaining for the plants and animals, it requires minimal inputs and yields valuable outputs. The five main inputs are water, oxygen, light, fish feed, and electricity (to pump, filter, and oxygenate the water).

 

The aquaponic systems does not need to discharge or exchange water. Its main feature is that it is able to recirculate and reuse water. Water is added only to replace water loss that occurs from absorption or transpiration by plants, evaporation into the air from surface water, or removal of biomass such as would occur in removing solid buildup. In fact, aquaponics uses just 2% of the water that a conventionally irrigated nickfarm requires for the same vegetable production! This means aquaponic systems would be the ideal provider of both crops and fish in areas where water or fertile land is scarce.

Although aquaponics relies on varying degrees of energy, conservation can be achieved by using alternative energy sources or reducing the number of pumps used by designing the system to allow for water to flow downwards as much as possible.

 

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Although there are large-scale commercial aquaponic systems (yay for them!) an aquaponic system can be built anywhere with few supplies and minimal care. Here are some links to constructing your own aquaponic system:

 

 

Constructing a Classroom Aquaponic System

~ Written by: Alexa Keeler ~

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