Aquaponics: 20,000 Pounds of Fish & 70,000 Pounds Of Vegetables On A ¼ Acre

Aquaponics has ancient roots although there is some debate on its first occurrence.

Aquaponics refers to any system that combines conventional aquaculture (raising aquatic animals such as fish, snails, crayfish or prawns in tanks) with hydroponics (cultivating plants in water) in a symbiotic environment.

In normal aquaculture, excretions from the animals being raised can accumulate in the water, increasing toxicity.

In an aquaponic system, water from an aquaculture system is fed to a hydroponic system where the by-products are broken down by nitrification bacteria into nitrates and nitrites, which are utilized by the plants as nutrients, and the water is then recirculated back to the aquaculture system.

So, aquaponics is the combination of aquaculture (fish farming) and hydroponics (growing plants in water only), in a carefully designed, hyper-productive closed-loop system.

There is no pesticide, no fungicide, no fertilizer, no watering the garden, no bending down to weed the garden, and you produce food year round, no matter the climate or soil conditions. This can work even in the Sahara Desert or in Antarctica!

As existing hydroponic and aquaculture farming techniques form the basis for all aquaponics systems, the size, complexity, and types of foods grown in an aquaponics system can vary as much as any system found in either distinct farming discipline.

Floating aquaponics systems on polycultural fish ponds were installed in China in more recent years on a large scale growing rice, wheat and canna lily and other crops, with some installations exceeding 2.5 acres (10,000 m2).

The development of modern aquaponics is often attributed to the various works of the New Alchemy Institute and the works of Dr. Mark McMurtry et al. at the North Carolina State University.

Inspired by the successes of the New Alchemy Institute, and the reciprocating aquaponics techniques developed by Dr. Mark McMurtry et al., other institutes soon followed suit. Starting in 1997, Dr. James Rakocy and his colleagues at the University of the Virgin Islands  researched and developed the use of deep water culture hydroponic grow beds in a large-scale aquaponics system.

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In addition, aquaponic gardeners from all around the world have gathered in online community sites and forums to share their experiences and promote the development of this form of prolific gardening as well as creating extensive resources on how to build your own home systems.

Recently, aquaponics has been moving towards indoor production systems. In cities like Chicago, entrepreneurs are utilizing vertical designs to grow food year round. These systems can be used to grow food year round with minimal to no waste.

1. Plants: hydroponics

In the picture above you see A Deep Water Culture hydroponics system where plants grow directly into the effluent rich water without a soil medium. Plants can be spaced closer together because the roots do not need to expand outwards to support the weight of the plant.

And in this picture you see a single plant placed into a nutrient -rich water channel in a Nutrient film technique (NFT) system.

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So, plants are grown as in hydroponics systems, with their roots immersed in the nutrient-rich effluent water.

This enables them to filter out the ammonia that is toxic to the aquatic animals, or its metabolites.

After the water has passed through the hydroponic subsystem, it is cleaned and oxygenated, and can return to the aquaculture vessels.This cycle is continuous.

Common aquaponic applications of hydroponic systems include:

  • Deep water raft aquaponics: styrofoam rafts floating in a relatively deep aquaculture basin in troughs.
  • Recirculating aquaponics: solid media such as gravel or clay beads, held in a container that is flooded with water from the aquaculture. This type of aquaponics is also known as closed-loop aquaponics.
  • Reciprocating aquaponics: solid media in a container that is alternately flooded and drained utilizing different types of siphon drains. This type of aquaponics is also known as flood-and-drain aquaponics or ebb-and-flow aquaponics.
  • Other systems use towers that are trickle-fed from the top, nutrient film technique channels, horizontal PVC pipes with holes for the pots, plastic barrels cut in half with gravel or rafts in them. Each approach has its own benefits.

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Since plants at different growth stages require different amounts of minerals and nutrients, plant harvesting is staggered with seedlings growing at the same time as mature plants. This ensures stable nutrient content in the water because of continuous symbiotic cleansing of toxins from the water.

2. Animals: aquaculture

Filtered water from the hydroponics system drains into a catfish tank for re-circulation.

Freshwater fish are the most common aquatic animal raised using aquaponics, although freshwater crayfish and prawns are also sometimes used. In practice,  tilapia are the most popular fish for home and commercial projects that are intended to raise edible fish amounts although many others  are also used.

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For temperate climates when there isn’t ability or desire to maintain water temperature, bluegill and catfish are suitable fish species for home systems.  Koi and goldfish may also be used if the fish in the system need not be edible.

Aquaponics operation system

The 5 main inputs to the system are water, oxygen, light, feed given to the aquatic animals, and electricity to pump, filter, and oxygenate the water. Spawn or fry may be added to replace grown fish that are taken out from the system to retain a stable system.

In terms of outputs, an aquaponics system may continually yield plants such as vegetables grown in hydroponics, and edible aquatic species raised in an aquaculture.

Typical build ratios are .5 to 1 square root of grow space for every 1 U.S. gal (3.8 liters) of aquaculture water in the system. 1 U.S. gal (3.8 L) of water can support between .5 lb (0.23 kg) and 1 lb (0.45 kg) of fish stock depending on the effective aeration and filtration.

Ten primary guiding principles for creating successful aquaponics systems were issued by Dr. James Rakocy, the director of the aquaponics research team at the University of the Virgin Island, based on extensive research done as part of the Agricultural Experiment Station aquaculture program. They are as follows:

  1. Use a feeding rate ratio for design calculations
  2. Keep feed input relatively constant
  3. Supplement with calcium, potassium and iron  
  4. Ensure good  aeration
  5. Remove solids
  6. Be careful with aggregates
  7. Oversize pipes
  8. Use biological pest control
  9. Ensure adequate  bio filtration
  10. Carefully and regularly control  pH value

Feed source

As in all aquaculture based systems, stock feed usually consists of fish meal derived from lower-value species. Ongoing depletion of wild fish stocks makes this practice unsustainable.

Organic fish feeds may prove to be a viable alternative that relieves this concern. Other alternatives include growing duckweed with an aquaponics system that feeds the same fish grown on the system, excess worms grown from vermiculture composting, using prepared kitchen scraps, as well as growing black soldier fly larvae to feed to the fish using composting grub growers.

Water usage

Aquaponic systems do not typically discharge or exchange water under normal operation, but instead recirculate and reuse water very effectively. The system relies on the relationship between the animals and the plants to maintain a stable aquatic environment that experience a minimum of fluctuation in ambient nutrient and oxygen levels.

Water is added only to replace water loss from absorption and transpiration by plants, evaporation into the air from surface water, overflow from the system from rainfall, and removal of biomass such as settled solid wastes from the system.

As a result, aquaponics uses approximately 2% of the water that a conventionally irrigated farm requires for the same vegetable production. This allows for aquaponic production of both crops and fish in areas where water or fertile land is scarce. Aquaponic systems can also be used to replicate controlled wetland conditions.

Constructed wetlands can be useful for bio filtration and treatment of typical household sewage. The nutrient-filled overflow water can be accumulated in catchment tanks, and reused to accelerate growth of crops planted in soil, or it may be pumped back into the aquaponic system to top up the water level.

Energy usage

Aquaponic installations rely in varying degrees on man-made energy, technological solutions, and environmental control to achieve recirculation and water/ambient temperatures. However, if a system is designed with energy conservation in mind, using alternative energy sources and a reduced number of pumps by letting the water flow downwards as much as possible, it can be highly energy efficient.

While careful design can minimize the risk, aquaponics systems can have multiple ‘single points of failure’ where problems such as an electrical failure or a pipe blockage can lead to a complete loss of fish stock.

The fish and plants you select for your aquaponic system should have similar needs as far as the temperature and the pH are concerned. There will always be some compromise to the needs of the fish and plants but, the closer they match, the more success you will have.

As a general rule, warm, fresh water, fish and leafy crops such as lettuce and herbs will do the best. In a system heavily stocked with fish, you may also have god luck with fruiting plants such as tomatoes and peppers.

Here is a list of fish that we have already raised in aquaponics with good results:

  • tilapia
  • blue gill/brim
  • sunfish
  • crappie
  • koi
  • fancy goldfish
  • pacu
  • various ornamental fish such as angelfish, guppies, tetras, swordfish, mollies

Other fish raised in our aquaponics system include:

  • carp
  • barramundi
  • silver perch, golden perch
  • yellow perch
  • Catfish
  • Largemouth Bass

And here is a list of plants that will do well in any aquaponic system:

  • any leafy lettuce
  • pak choi
  • kale
  • swiss chard
  • arugula
  • basil
  • mint
  • watercress
  • chives
  • most common house plants

Plants that have higher nutritional demands and will only do well in a heavily stocked, well established aquaponic system:

  • tomatoes
  • peppers
  • cucumbers
  • beans
  • peas
  • squash
  • broccoli
  • cauliflower
  • cabbage

Note well: Using this system, each 25 SF of grow space can feed one adult 25% of their protein and all of their table vegetables, year round, forever, just like a perpetuum mobile!