Purdue University Study On The Aquaponics System

Aquaponics – Purdue University

It’s a 21st century reality that environmental concerns have had been impacting all areas of the US economy, including agriculture. Environmental awareness has created increase consumer interest in locally grown sustainable food production; while advances in technology continue to improve farming productivity and efficiency. It still requires a large amount two very precious natural resources, water and land. However there is a sustainable financially viable food production system; that utilizes approximately 2 % of the water use of the conventional farm. This system combines fish farming and hydroponics, to create a semiotic environment known as aquaponics.


Aquaponics brings together the practices of aquaculture raising fish and tanks with hydroponics; the practice of growing plants in a soil less environment. In an aquaculture system, waste accumulates in the tank which eventually has to be removed; to maintain the health of the fish. This bi-product contains rich nutrients that plants filter out; which allows the water to be recycled and sent back to the fish tanks to start the process all over again. An aquaponics system is scalable from small individual use, all the way up to a large commercial operation. An initial investment for equipment can range from a few thousand dollars to several thousand depending on the size of the operation. Keep in mind, for every gallon of water in your fish tank, you can have one half to one square feet of grow beds space depending on fish intensity; that feeding rates and for every one pound of fish to be raised you need one to two gallons of water.

The fish farming aspect of aquaponics is based on the eco-friendly recirculating aquaculture system. A recirculating system is an indoor system that allows for careful control of the fishes environment year round. While there are economic advantages of not being affected by the outside elements there is a higher initial investment; of equipment than they would be for caged or pond farming. In the recirculating system all proper fish husbandry practices supply. Water quality we maintain and carefully monitor consistent testing of water quality is a must to keep the fish healthy of disease free. Access to water and reliable electricity is crucial for success; even though the water is being recirculated, run off and evaporation will occur. The water supply will need to be occasionally replenished, electricity or some sort of power is necessary; to keep the fish tank at the ideal temperature and run pumps, to circulate water back between tanks.

This type of optimal condition allows for a fast growing stock that is less susceptible to disease; but regular observation is still an important factor in maintaining fish health, any behavioral changes particularly during feeding is an indicator of problems. The feed you use will be determined by the type of specie you choose to raise, but whichever feed you select it must provide a complete diet and be of the floating variety and auto or demand feeder is frequently used in the recirculating environment. Even though the feeding process is automated you still want to be present to observe the feeding behavior. Tilapia is the most common specie raised in the recirculating system; because of its large size, rapid growth, high density and hardiness. Perch, Hybrid Striped Bass, Trout and Catfish are also known to do well in the tank environment.

Each species of fish is going to have their own set of guidelines for proper feed amounts. Harvest-fish will be determined; by the individual specie growth cycle. Be sure to practice proper fish handling of the harvesting in the transportation of the fish to the market. For additional guidance, watch this online video or contact your local county extension office, for additional guidance. The key component to the recycling aquaculture system; is the removal of the harmful waste products and uneven food from the rearing tanks, while continuing to recycle the water. Instead of disposing of this material which you would do on a strictly aqua cultural system; the practice of aquaponics utilizes the fish effluent in the growing of plants in a hydroponic setting; as the waste and the uneven food collected at the bottom of the rearing tanks. It exits by way of PVC pipe to a clarifier or a settler.

A clarifier or a settler is where the anaerobic mineralization of the waste and uneven food occur. Overtime the waste material collected in the clarifier begins to break down and releases nutrients to the water. Trace material such as iron may have to be added to supplement the plants nutritional needs. This mineral rich water then moves through the bio-filter; a bio-filter allows for the natural biological process called nitrification to occur through the breakdown of the waste. Large amount of ammonia are released in the water, the natural bacteria present in the water will use the oxygen in an aerobic process; to efficiently convert the ammonia to nitrite and then to nitrate.

The bio-medium in the bio filter expedites the process by allowing the bacteria to colonize in an area with direct water temperature, ph. and dissolve oxygen levels. This nitrate rich water then moves to the plant grow beds; the grow beds can be a soil less environment; or they may be using a growing medium like perlite or ceramic stones. The plant roots are immerse in the water absorbing the rich nutrients while simultaneously; filtering out the nitrogenous compounds that are toxic to the fish. Within the hydroponics discipline of aquaponics, there are a few different growing methods that you can choose from.

aquaponics_systemDeep water raft aquaponics uses Styrofoam mats to secure the plants in a trough of water. The seedlings are placed in net pots with the planting medium; like the cocoa peat a material from the outer shell of a coconut. Cocoa peat stimulates and protects root growth, but contains no mineral, the plants can be grown to maturity in that pots or can be removed from that pots in growing mediums; after a couple of weeks and placed in a different floating mat, to maximize space in the growing beds. Plants can also be grown in a solid medium like gravel or perlite. The aqua culture water floods the grow bed containing the plants in growing medium; this type of system is known as recirculating aquaponics or closed-loop aquaponics.

A common growing medium used is perlite; perlite is a volcanic rock that provides superior root growth by absorbing the nutrient rich water, and keeping the moisture level constant and consistent throughout the plants root system. Depending on the growing technique, there are several medium options to choose from. Seek out all available literature and contact your local extension office for additional guidance. Water is only half the equation, when it comes to plant growth; the other of course is light. Your lighting needs will depend on your location of your aquaponics system; in the mid-west where systems are in doors artificial lights will be necessary.

There are several types of lights that can be used depending on the budget and application; high up with fluorescents’ are commonly used grow lights. It’s a cost effective option with the added benefit of having low heat output; this allows for very close light placement which provides for maximum plant growth. LED grow lights are much more expensive than florescent use 2-3 times the cost or more power efficient, have longer lasting bulbs and have the flexibility of adjusting the lights spectrum. Red light is more desirable for budding plants; while blue light works better for vegetative growth. It’s possible to mitigate the cost of LED lights; by installing a track system above the grow beds and reducing the number of light fixtures needed.

Obviously there is a tradeoff, the growth rate of a plant under a constant source of light will be faster than a grow bed utilizing the track system. Metal highlights light are also used in an aquaponics system, these grow lights put on an intense amount of light high in the blue spectrum. The individual bulbs can be expensive and they do produce a considerable; amount of heat so you need to be sure that your space has proper cooling and ventilation. Metal highlights are best for large plants, while fluorescents, do better with small leafy plants. Also you want to avoid using metal highlights on seedlings, due to the intensity of the light; grow lights can be used as the sole source of light or combine with natural light in a greenhouse environment. A greenhouse provides economic advantages by reducing the amount of artificial light required.

Like selecting the species of fish, choosing what plants to grow is an important decision that affects the infrastructure and business planning. Leafy greens, like lettuce and cabbage and herbs like basil and regna do well in an aquaponics system; but any common garden vegetable can be grown. Careful consideration must be given with plants selection, because in an aquaponics operation the plant side tends to generate more income. Study the markets and choose plants that will bring the largest profit margin. Focusing on markets that will pay a premium for organically growing vegetables; like farmers market and stores that specialized in natural and organic food, packaging your own product is also an option.

For more information on plants, seek out additional literature and contact your local extension office for guidance. As the water moves through the grow bed and the plants pull out the nutrients; the filter water flows to the bed to the lowest point in the system called a sap. From there the water is pumped back into the rearing tanks and the cycle continues. Some micronutrients such as iron and magnesium may need to be added, to the system to ensure plant health.

Aquaponics reduces the environmental footprint in crop production and allows for cultivating plants in locations you don’t typically associate with farming. From a windowless basement to a remodeled urban town house, to a retrofitted factory building; as long as there is access to electricity and water, fish and crops can be raised in this indoor ecofriendly semiotic environment. However, with the ability to raise fish and grow plants indoor year round; a major issue to consider is the energy cost associated with heating and air conditioning. HBAC is one of the biggest expenses in an aquaponics operation, making sure the building is well insulated, will cut down on this cost. Water temperature needs to be maintained for the health of the fish and room temperature needs to be regulated for plant growth.

Each aquaponics systems can be designed to maximize the use of available space. A room with high ceilings can allow for the stocking of grow beds; this will require more pumps and plumbing, but he investment will allow for more plant production. Utilizing natural light from existing windows, and an old factory building; can also help by reducing artificial lighting cost. With careful planning and care taking aquaponics, can not only be an eco-friendly sustainable food production system; but a profitable business with significant growth potential. This video has provided an introduction into aquaponics; if you are thinking about starting your own operation, seek out additional information on the web and or contact your local extension office for guidance.

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