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.[1]
<https://en.wikipedia.org/wiki/Aquaponics#cite_note-UVI-1>
Contents
The first aquaponics research in Canada
<https://en.wikipedia.org/wiki/Canada> was a small system added onto
existing aquaculture research at a research station in Lethbridge
<https://en.wikipedia.org/wiki/Lethbridge>, Alberta
<https://en.wikipedia.org/wiki/Alberta>. Canada saw a rise in aquaponics
setups throughout the ’90s, predominantly as commercial installations
raising high-value crops such as trout and lettuce. A setup based on the
deep water system developed at the University of Virgin Islands was built
in a greenhouse at Brooks, Alberta
<https://en.wikipedia.org/wiki/Brooks,_Alberta> where Dr. Nick Savidov and
colleagues researched aquaponics from a background of plant science. The
team made findings on rapid root growth in aquaponics systems and on
closing the solid-waste loop, and found that owing to certain advantages in
the system over traditional aquaculture, the system can run well at a low
pH level, which is favoured by plants but not fish.
Parts of an aquaponic system
<https://en.wikipedia.org/wiki/File:Aquaponics_at_Growing_Power,_Milwaukee.jpg>
A commercial aquaponics system. An electric pump moves nutrient-rich water
from the fish tank through a solids filter to remove particles the plants
<https://en.wikipedia.org/wiki/Plants> above cannot absorb. The water
<https://en.wikipedia.org/wiki/Water> then provides nutrients for the
plants and is cleansed before returning to the fish tank below.
Depending on the sophistication and cost of the aquaponics system, the
units for solids removal, biofiltration, and/or the hydroponics subsystem
may be combined into one unit or subsystem,[14]
<https://en.wikipedia.org/wiki/Aquaponics#cite_note-srac-14> which prevents
the water from flowing directly from the aquaculture part of the system to
the hydroponics part. By utilizing gravel or sand as plant supporting
medium, solids are captured and the medium has enough surface area for
fixed-film nitrification. [14]
<https://en.wikipedia.org/wiki/Aquaponics#cite_note-srac-14> The ability to
combine biofiltration and hydroponics allows for aquaponic system to in
many cases eliminate the need for an expensive, separate biofilter.
Live components
Many plants are suitable for aquaponic systems, though which ones work for
a specific system depends on the maturity and stocking density of the fish.
These factors influence the concentration of nutrients from the fish
effluent, and how much of those nutrients are made available to the plant
roots via bacteria.
Other plants, such as tomatoes, cucumbers, and peppers, have higher
nutrient requirements and will only do well in mature aquaponic systems
that have high stocking densities of fish.[16]
<https://en.wikipedia.org/wiki/Aquaponics#cite_note-:0-16>
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 <https://en.wikipedia.org/wiki/Deep_water_culture>
aquaponics*: styrofoam <https://en.wikipedia.org/wiki/Styrofoam> rafts
floating in a relatively deep aquaculture basin in troughs. Raft tanks can
be constructed to be quite large, and enable seedlings to be transplanted
at one end of the tank while fully grown plants are harvested at the other,
thus ensuring optimal floor space usage. [20]
<https://en.wikipedia.org/wiki/Aquaponics#cite_note-:2-20>
- *Recirculating aquaponics*: solid media such as gravel
<https://en.wikipedia.org/wiki/Gravel> or clay
<https://en.wikipedia.org/wiki/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*.
- *Nutrient film technique
<https://en.wikipedia.org/wiki/Nutrient_film_technique> channels:*
plants are grown in lengthy narrow channels, with a film of nutrient-filled
water constantly flowing past the plant roots. Due to the small amount of
water and narrow channels, helpful bacteria cannot live there and therefore
a bio filter is required for this method. [20]
<https://en.wikipedia.org/wiki/Aquaponics#cite_note-:2-20>
- Other systems use towers that are trickle-fed from the top, horizontal
PVC <https://en.wikipedia.org/wiki/Polyvinyl_chloride> pipes with holes
for the pots, plastic barrels cut in half with gravel or rafts in them.
Each approach has its own benefits.[21]
<https://en.wikipedia.org/wiki/Aquaponics#cite_note-21>
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.[22] <https://en.wikipedia.org/wiki/Aquaponics#cite_note-22>
Biofilter
In an aquaponics system, the bacteria responsible for the conversion of
ammonia to usable nitrates for plants form a biofilm
<https://en.wikipedia.org/wiki/Biofilm> on all solid surfaces throughout
the system that are in constant contact with the water. The submerged roots
of the vegetables combined have a large surface area where many bacteria
can accumulate. Together with the concentrations of ammonia and nitrites in
the water, the surface area determines the speed with which nitrification
takes place. Care for these bacterial colonies is important as to regulate
the full assimilation of ammonia and nitrite. This is why most aquaponics
systems include a biofiltering unit, which helps facilitate growth of these
microorganisms <https://en.wikipedia.org/wiki/Microorganism>. Typically,
after a system has stabilized ammonia
<https://en.wikipedia.org/wiki/Ammonia> levels range from 0.25 to 2.0 ppm;
nitrite levels range from 0.25 to 1 ppm, and nitrate levels range from 2 to
150 ppm.[*citation needed
<https://en.wikipedia.org/wiki/Wikipedia:Citation_needed>*] During system
startup, spikes may occur in the levels of ammonia (up to 6.0 ppm) and
nitrite (up to 15 ppm), with nitrate levels peaking later in the startup
phase.[*citation needed
<https://en.wikipedia.org/wiki/Wikipedia:Citation_needed>*] Since the
nitrification process acidifies the water, non-sodium
<https://en.wikipedia.org/wiki/Sodium> bases such as potassium hydroxide
<https://en.wikipedia.org/wiki/Potassium_hydroxide> or calcium hydroxide
<https://en.wikipedia.org/wiki/Calcium_hydroxide> can be added for
neutralizing the water's pH <https://en.wikipedia.org/wiki/PH>[14]
<https://en.wikipedia.org/wiki/Aquaponics#cite_note-srac-14> if
insufficient quantities are naturally present in the water to provide a
buffer against acidification. In addition, selected minerals or nutrients
such as iron can be added in addition to the fish waste that serves as the
main source of nutrients to plants.[14]
<https://en.wikipedia.org/wiki/Aquaponics#cite_note-srac-14>
A good way to deal with solids buildup in aquaponics is the use of worms,
which liquefy the solid organic matter so that it can be utilized by the
plants and/or other animals in the system. For a worm-only growing method,
please see Vermiponics <https://en.wikipedia.org/wiki/Vermiponics>.
Operation
The five 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 <https://en.wikipedia.org/wiki/Spawn_%28biology%29> or fry
<https://en.wikipedia.org/wiki/Juvenile_fish> 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 foot
<https://en.wikipedia.org/wiki/Square_foot> of grow space for every
1 U.S. gal (3.8 L) 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 aeration <https://en.wikipedia.org/wiki/Aeration> and
filtration.[23]
<https://en.wikipedia.org/wiki/Aquaponics#cite_note-purdue-23>
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
<https://en.wikipedia.org/wiki/Alternative_energy> 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.
Fish stocking
In order for aquaponic systems to be financially successful and make a
profit whilst also covering its operating expenses, the hydroponic plant
components and fish rearing components need to almost constantly be at
maximum production capacity. [14]
<https://en.wikipedia.org/wiki/Aquaponics#cite_note-srac-14> To keep the
bio-mass of fish in the system at its maximum (without limiting fish
growth), there are 3 main stocking method that can help maintain this
maximum.
- *Sequential rearing:* Multiple age groups of fish share a rearing
tank, and when an age group reaches market size they are selectively
harvested and replaced with the same amount of fingerlings. [14]
<https://en.wikipedia.org/wiki/Aquaponics#cite_note-srac-14> Downsides
to this method include stressing out the entire pool of fish during each
harvest, missing fish resulting in a waste of food/space, and the
difficulty of keeping accurate records with frequent harvests.[14]
<https://en.wikipedia.org/wiki/Aquaponics#cite_note-srac-14>
- *Stock splitting:* Large quantities of fingerlings are stocked at once
and then split into two groups once the tank hits maximum capacity, which
is easier to record and eliminates fish being "forgotten". A stress-free
way of doing this operation is via "swimways" that connect various rearing
tanks and a series of hatches/moving screens/pumps that move the fish
around. [14] <https://en.wikipedia.org/wiki/Aquaponics#cite_note-srac-14>
- *Multiple rearing units:* Entire groups of fish are moved to larger
rearing tanks once their current tank hits maximum capacity. Such systems
usually have 2-4 tanks that share a filtration system, and when the largest
tank is harvested, the other fish groups are each moved up into a bigger
tank whilst the smallest tank is restocked with fingerlings. [14]
<https://en.wikipedia.org/wiki/Aquaponics#cite_note-srac-14> It is also
common for there to be several rearing tanks yet no ways to move fish
between them, which eliminates the labor of moving fish and allows each
tank to be undisturbed during harvesting, even if the space usage is
inefficient when the fish are fingerlings. [14]
<https://en.wikipedia.org/wiki/Aquaponics#cite_note-srac-14>
Ideally the bio-mass of fish in the rearing tanks doesn't exceed 0.5
lbs/gallon, in order to reducing stress from crowding, efficiently feed the
fish and promote healthy growth. [14]
<https://en.wikipedia.org/wiki/Aquaponics#cite_note-srac-14>
Disease and pest management
Although pesticides can normally be used to take care of insect on crops,
in an aquaponic system the use of pesticides would threaten the fish
ecosystem. On the other hand, if the fish acquire parasites or diseases,
therapeutants cannot be used as the plants would absorb them. [14]
<https://en.wikipedia.org/wiki/Aquaponics#cite_note-srac-14> In order to
maintain the symbiotic relationship between the plants and the fish,
non-chemical methods such as traps, physical barriers and biological
control (such as parasitic wasps/ladybugs to control white flies/aphids)
should be used to control pests. [14]
<https://en.wikipedia.org/wiki/Aquaponics#cite_note-srac-14>
Economic viability
The Caribbean island of Barbados <https://en.wikipedia.org/wiki/Barbados>
created an initiative to start aquaponics systems at home, with revenue
generated by selling produce to tourists in an effort to reduce growing
dependence on imported food.
The Smith Road facility in Denver started pilot program of aquaponics to
feed 800 to 1000 inmates at Denver Jail and neighboring downtown facility
which consist of 1,500 inmates and 700 officers.
Volunteer operation in Nicaragua “Amigos for Christ” manages its plantation
for feeding 900+ poverty-stricken school children by using nutrients from
aquaponics method.[37]
<https://en.wikipedia.org/wiki/Aquaponics#cite_note-37>
Verticulture in Bedstuy utilizes old Pfizer manufacturing plant for
producing basil in commercial scale through aquaponics, yielding 30-40
pounds of basil a week.[39]
<https://en.wikipedia.org/wiki/Aquaponics#cite_note-39>
Aquaponics startup Edenworks in New York expands to full-scale commercial
facility, which will generate 130,000 pounds of greens and 50,000 pounds of
fish a year. [40] <https://en.wikipedia.org/wiki/Aquaponics#cite_note-40>
In addition, aquaponic gardeners from all around the world are gathering in
online community sites and forums to share their experiences and promote
the development of this form of gardening[44]
<https://en.wikipedia.org/wiki/Aquaponics#cite_note-44> as well as creating
extensive resources on how to build 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.[45]
<https://en.wikipedia.org/wiki/Aquaponics#cite_note-45>
There are various modular systems made for the public that utilize
aquaponic systems to produce organic vegetables and herbs, and provide
indoor decor at the same time.[46]
<https://en.wikipedia.org/wiki/Aquaponics#cite_note-46> These systems can
serve as a source of herbs and vegetables indoors. Universities are
promoting research on these modular systems as they get more popular among
city dwellers.[47] <https://en.wikipedia.org/wiki/Aquaponics#cite_note-47>
References