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Journal of Agricultural, Environmental and Consumer Sciences - Vol. 19, 2019, 5-13
Review of Aquaponics System: Searching for a Technically
Feasible and Economically Profitable Aquaponics System
Kamal Gosh1* and Santa Chowdhury2
1Department of Aquaculture and Fisheries, University of Arkansas at Pine Bluff
1200 North University Drive, Pine Bluff, Arkansas, USA 71601
2Department of Botany, University of Chittagong
Chittagong, Bangladesh 2410
*Email: goshk@uapb.edu
SUMMARY
Concerns regarding population growth and
resource scarcity have led to a recent
renaissance of food production research.
Over the past few decades, scientists have
discovered new and innovative methods for
growing food that, cumulatively, may hold
the key to feed an ever-increasing world
population both efficiently and sustainably.
Aquaponics has shown promising as being a
sustainable solution for producing food
locally in all parts of the world. Although
many studies have shown aquaponics food
production to be feasible, there are relatively
few studies that address the overall technical
and economic feasibility of the aquaponics in
United States of America. This review study
is, therefore, conducted to find out the overall
feasibility of aquaponics system in current
commercial settings. Current review study
showed that Deep-Water Culture system
(DWC) and Nutrient Film Technique (NFT)
could be the good option to adopt at a
commercial scale. Lettuce, herbs, and
specialty greens (such as spinach, chives,
basil, and watercress) are suggested as they
have low to medium nutritional requirements
and are well adapted to the aquaponics
system. The vegetables yielding plants (such
as tomatoes, bell peppers, and cucumbers)
have a higher nutritional demand and
perform better in a heavily stocked, well-
established aquaponics system. Among the
warm and cold-water species, tilapia, trout,
perch, arctic char, and bass are well adapted
to Recirculating Aquaculture System (RAS).
Tilapia is highly favored in the commercial
aquaponics system due to their high adaptive
nature and tolerating capacity in fluctuating
water conditions. Vegetables and other plants
derived from the hydroponic system is likely
to be more profitable than the fish produced
from the recirculating aquaculture system.
INTRODUCTION
Aquaponics is the integration of recirculating
aquaculture and hydroponics systems (soil-
less) that is used for fish and crop production.
It has been gaining attention (Rakocy et al.
2006) as it serves as a bio-integrated model
for sustainable food production (Diver 2006).
This technology was initially adopted by the
researchers from the New Alchemy Institute
North Carolina State University during late
1970 and early 1980s. University of the
Virgin Islands (UVI) had adopted this
technology later in 1980. Review study
showed that aquaponics has been receiving
Journal of Agricultural, Environmental and Consumer Sciences - Vol. 19, 2019, 5-13
attention since then (Love et al. 2014), and
the adoption rate of this system is increasing.
The potential reason for such outcome is the
interlinking of aquacultural and hydroponic
procedures that represent the system as a
promising and sustainable food production
method (Goddek et al. 2015). This system
can also ensure the protein security to the
ever-growing urban population that demands
animal protein in the future (Alexandratos
and Bruinsma 2012). However, the future of
conventional farming, including the intensive
animal protein production, in meeting this
demand is challenged by fluctuating energy
prices, growth variability issue, and
marketing problem. Likewise, resource
scarcities such as decreasing the arable
surfaces, constrained freshwater supplies,
soil degradation, and soil nutrient depletion
also add an extra layer to these challenges
(Bindraban et al. 2012;.Klinger and Naylor
2012) This alerts the researchers to take the
corrective action to compensate the existing
shortfall of fish production through
aquaponics system. Review study showed
that aquaponics system is likely to be a good
option to solve such problem, but the
feasibility of such system has not yet been
fully realized either cost-effectiveness or
technical capabilities point of views (Rakocy
2012). In such situation, this paper reviews
the scientific literature of technical feasibility
and economic profitability of the aquaponics
system and demonstrates which system will
be suitable for adoption in the commercial
settings. The purpose of this paper is to
highlight the principals, designs, challenges,
and economics of aquaponics system and
give directions to the researchers and
entrepreneurs to meet the goal of establishing
large-scale economically viable aquaponics
system in the USA.
Principals of Aquaponics
The basic principles under aquaponics are; a)
the waste products from one biological
system can be used as a nutrient for the other
biological system (Fig. 1); b) integration of
fish and plant culture can lead to produce
multiple products in one time; c) water can be
re-used through biological filtration and
recirculation processes; d) local food
production system provides access the
healthy foods and enhances the local
economy (Diver 2006).
In the aquaponics system, nutrient-rich
effluent from fish tanks is used to fertigate the
hydroponic production beds (Diver 2006).
This is certainly good for the fish health,
plant roots and rhizobacteria that can remove
the nutrients from the water (Diver 2006).
These nutrients, generated from the fish
manure, algae, and decomposing fish feed,
are contaminants that would otherwise build
up toxicity in the fish tanks and may likely to
deteriorate the water quality parameters
detrimental to the fish population (Diver
2006). In contrast, the hydroponic beds
function as a biofilter by stripping off the
ammonia, nitrates, nitrites, and phosphorus
and therefore, the freshly cleansed water can
be re-used for fish population (Diver 2006).
The nitrifying bacteria living in the gravel (in
association with the plant roots) play a
critical role in nutrient cycling and without
these microorganisms, the whole system
would stop functioning (Diver 2006).
Journal of Agricultural, Environmental and Consumer Sciences - Vol. 19, 2019, 5-13
Figure 1. Symbiotic aquaponics cycle
Aquaponics: Key Elements and
Considerations
Aquaponics system is developed by creating
the connection between a Recirculating
Aquaculture System (RAS) and hydroponic
components. The water, hereafter, circulates
from the fish tank to filtration units, before it
pumped into the hydroponic beds that are
used as water reprocessing units (Fig 2). The
filtration part is composed of mechanical
filtration unit for solid particles removal (e.g.,
drum filter or settling tank), and biofilters for
nitrification processes (e.g., trickling or
moving bed biofilter). This configuration and
complexity are, however, varied among the
systems.
Hydroponic System and its Bed
It produces plants in a soilless medium,
where the nutrients supplied to the crop are
dissolved in water. In general, three types of
hydroponic beds are commonly used. A
comparative study of these hydroponic beds
versus soil culture is presented below (Table
1)
Figure 2. Basic aquaponics system layout
Fish
Nutrient-rich
effluents resulted
from fish feed &
fish metabolism
Bacteria
Nitrification
Plants
Fish section Mechanical/bio-filter
section Sump Pump Plant section
Journal of Agricultural, Environmental and Consumer Sciences - Vol. 19, 2019, 5-13
Table 1. Structure, advantages, disadvantages and nutrient uptake of different hydroponic beds
Media-based grow
bed (MGB)
Deep-Water Culture
system (DWC)
Nutrient Film
Technique (NFT)
Soil
Structure
A hydroponic trough
filled with inert
substrate (e.g.,
expanded clay, perlite,
pumice, gravel), serving
as root support and a
microbial substrate.
A large trough with
perforated floating
rafts, where net plant
pots (are filled with
media, e.g., rock wool,
coco or pumice that
support roots) are
inserted.
A narrow channel of
perforated squared
pipes where the roots
are partially immersed
in a thin layer of
streaming water.
Traditional system
where the soil is
used as the prime
medium for plant
production
Advantages
Media serves as
substrate for nitrifying
bacteria
Constant water flow
Constant water flow
Less infrastructure
Act as a solid filtering
medium
Small sump tank
needed
Small sump tank
needed
Natural roots
environment
Mineralization in grow
bed
Ease of maintenance
and cleaning
Require a smaller
volume of water
Colonized by
microflora and
fungi
Colonized by a broad
microflora
-
Light infrastructure
An “organic way
of production”
Disadvantages
Maintenance and
cleaning difficult
Require a large volume
of water
Separate biofilter
needed
Small control on
soil nutrient
Clogging lead to
inefficient biofiltration
Heavy hydroponic
infrastructure
Expensive material
Vulnerable to
disease
Heavy hydroponic
infrastructure
Device for roots
aeration mandatory
Lower yields
Lower basil and
okra yield
Nutrient uptake
High
High
Lower
Lower
Sources
Lennard and Leonard
(2006)
Rakocy and Hargreaves
(1993)
Lennard and Leonard
(2006)
Rakocy and Hargreaves
(1993)
Nicola et al. (2007)
Lennard and Leonard
(2006)
Bulgarelli et al.
(2013)
Rakocy et al.
(2006)
Journal of Agricultural, Environmental and Consumer Sciences - Vol. 19, 2019, 5-13
Plant Selection
The selection of plant species adapted to
hydroponic culture (in aquaponics system) is
related to the stocking density of fish and
subsequent nutrient concertation of
aquacultural effluent. In general, lettuce,
herbs, and specialty greens (spinach, chives,
basil, and watercress) have low to medium
nutritional requirements and are well adapted
to the aquaponics system (Diver 2006).
Vegetables yielding plants (tomatoes, bell
peppers, and cucumbers) have a higher
nutritional demand and perform better in a
heavily stocked, well-established aquaponics
system (Diver 2006). Greenhouse varieties of
tomatoes are better adapted to low light with
high humidity conditions in greenhouses than
field varieties (Diver 2006).
Fish Selection
Among the warm and cold-water species,
tilapia, trout, perch, Arctic char, and bass are
well adapted to recirculating aquaculture
system (RAS) (Diver 2006). However, tilapia
is the most favored and adapted species in the
commercial aquaponics system in North
America (Diver 2006). This is mostly due to
their adaptive nature and tolerating capacity
in fluctuating water conditions such as pH,
temperature, oxygen, and dissolved solids
(Diver 2006).
Aquaponics Designs
Review study shows that the aquaponics
system can be designed in several ways based
on its hydrological and functional
configuration. A comparative review study of
such system is mentioned below in Table 2.
It is noted that media-based aquaponics
system is not included in this comparative
study as the production intensification
strategy cannot be applied for this system (at
the commercial level) (Table 2). This method
is mainly suitable for hobby or for class
project performed at school/college level.
Technical Challenges
The management of the aquaponics system is
quite complex as it deals with three different
concepts of fish, plant, and microorganism
together. Failure to maintain a unique water
quality parameter, particularly the pH
stabilization may jeopardize the whole
system that may lead to the massive killing of
fish, plant and beneficial microbes together.
In general, the pH requirement for most of the
plant species is ranged from 6 to 6.5 to
enhance the nutrient uptake (Goddek et al.
2015). Fish, in contrast, need a pH range of
7-9 to show the best growth performance
(Boyd 1998). The nitrifying bacteria requires
a high pH level (>7). In general, three types
of bacteria are playing the critical role in this
nitrification process and their optimal pH
levels are ranged from 7.5 (Keen and Prosser
1987), 7.0-7.5 (Hatayama et al. 2000) and
8.0-8.3 (Blackburne et al. 2007) for
Nitrobacter, Nitrosomonas and Nitrospira,
respectively. Therefore, the ideal pH range
applicable for this whole aquaponics system
is 6.0-8.0. Maintaining this pH range is quite
critical in stabilizing the water quality
parameters in this aquaponics system.
Journal of Agricultural, Environmental and Consumer Sciences - Vol. 19, 2019, 5-13
Table 2. A comparative study of different aquaponics designs and key parameters
System Type
Nutrient Film Technique (NFT)
Deep Water Culture (DWC)
Source
Adler et al. (2000)
Rakocy et al. (2004)
Rakocy et al. (2004a)
Location
Virginia., USA
University of Virgin
Islands, USA
Volume RAS (m3)
>38
43
Size hydroculture
(m2)
498
220
Plant density
(pcs/m2)
5.7/meter of NFT trays
8 (basil); 2–4 (okra)
Fish density (kg/m3)
113.4
61.5–70.7
Feed /plant growing
area (g/day/m2)
Not studied
81.4–99.6
Fish: plant ratio (kg)
Not studied
Not studied
Plants used
Basil (Ocimum basilicum); Lettuce
(Lactuca sativa L. “Ostinata”)
Basil (Ocimum basilicum);
Okra (Abelmoschus
esculentus)
Fish used
Rainbow Trout (Oncorhynchus
mykiss)
Nile Tilapia (Oreochromis
niloticus L.)
Biofiltration
Fluidized Sand Filter + Carbon
Dioxide Strippers
Net Filter
pH
7.2
7.0–7.5
Experimental period
Not studied
28 weeks (basil); 11.7 weeks
(Okra)
Investment cost ($
U.S.)
$100,120 (hydroponic part)*
Not studied
Annual total cost
($ U.S.)
$204,040 (lettuce);
$194,950 (basil)
$24,440 (tilapia + basil)
Break-even price
($ U.S.)
$13.80 (/case lettuce)a;
$0.53 (/basil)
$3.23 (/kg tilapia);
$1.66 (/kg basil)
Annual net return
($ U.S.)
$12,350–$44,350 (lettuce: $14–
$16/case)a; $27,750–$66,090 (basil:
$0.60–$0.70)
$116,000 (tilapia: $5.50/kg;
basil: $22.50/kg)
*Economic analysis is considered for the hydroponic part; a One case of lettuce typically contains
24 heads of lettuce.
Journal of Agricultural, Environmental and Consumer Sciences - Vol. 19, 2019, 5-13
Nutrient balance is another important aspect,
which is derived mostly from the fish feed
after finishing the chemical
reaction/nitrification process. This feed can
be divided into assimilated feed, uneaten feed
and soluble and sold fish excreta (Montanhini
Neto and Ostrensky 2015). Soluble excreta
are mainly the ammonia and are the most
available mineral until it is successively
transformed into nitrite and nitrate by
nitrifying bacteria (Lekang and Kleppe 2000;
Chen et al 2006). Here the uneaten feed and
solid faces need to be solubilized from
organic material to ionic mineral forms that
are easily assimilated by plants. The
solubilization rate usually varies among
minerals and do not accumulate equally
(Seawright et al. 1998; Rakocy and
Hargreaves 1993), which influences their
concentration in the water. Review study for
current practices in RAS suggested that the
solid wastes could be partially solubilized if
they were mechanically filtered out on a daily
basis (Cripps and Bergheim 2000). These
filtered wastes can be mineralized externally
and reinserted into the hydroponic beds
(Goddek et al. 2015). Review study also
showed that the physical and chemical
mechanisms of solubilization of all involved
microorganisms were not yet fully realized
and understood (van Rijn 2013). Hence, more
research is needed on fish waste
solubilization with the objective to transform
all added nutrients into plant biomass.
Maintaining the phosphorus balance is also
critical as this macro-nutrient is essential for
both vegetative and flowering stages of plant
growth. Among other technical challenges,
pest and disease management need special
attention as the conventional pesticides
cannot be used in aquaponics system as it
may create toxicity for the fish and other
desired biofilm production (e.g., autotrophic
nitrifying biofilm). In the same manner, use
of antibiotics and fungicides for fish
pathogen control are not suggested as it may
be lethal for the plant growth, nitrifying
biofilm and other nutrient solubilizing
microorganisms. These constraints demand
innovative research for unique pest and
disease management solution that minimize
the harmful impacts on the fish, plants, and
microorganisms.
Economic Challenges
In developing the aquaponics system, certain
key economic points must be considered to
make this system profitable. These include
(Engle 2015); 1) the overall investment
required to construct facilities and to
purchase necessary equipment (investment
cost); 2) the annual costs to operate the
system; and 3) realistic estimates of market
prices, In general, the production cost of fish
in an indoor system is two to three times
higher than growing fish at the outdoor/ponds
(Engle 2015). Hence, suitable market
development for this kind of indoor products
(i.e., produced at aquaponics system) is
important, where the consumers’ willingness
to pay will be a little higher than the average
market/market price (Engle 2015). Besides
these, the production cost is usually higher
for producing fish in recirculating
aquaculture unit compared to producing
vegetables from the hydroponic unit that may
lead to incur a net profit loss for the
aquaponics system. These are evidenced
from the review study, which is summarized
below (Table 3).
Journal of Agricultural, Environmental and Consumer Sciences - Vol. 19, 2019, 5-13
Table 3. Estimated costs of production for plants and fish raised in aquaponics as compared to
relevant market prices
Sources
Baker
(2010)
Bailey et al.
(1997)
Rakocy and Bailey
(1998)
Tokunaga
et al. (2015)
English
(2015)
Location
Hawaii
Virgin
Islands
Virgin Islands
Hawaii
Arkansas
Plant type
Lettuce
Lettuce
Lettuce
Basil
Lettuce
Lettuce
Production
cost
$3.31/kg
$11.14–
$12.40/casea
$6.15/case
$1.65/kg
Not studied
$1.02/head
Market
price
Not
studied
$20/case
$20/case
$22.49/kg
$ 4.74 /kg
$5.67/kg
Fish type
Tilapia
Tilapia
Tilapia
Tilapia
Tilapia
Tilapia
Production
cost
$11.00/kg
$6.99–
$8.33/kg
$3.22/kg
$5.51/kg
Not studied
$10.39/kg
Market
price
Not
studied
$5.51/kg
$ 3.22/kg
$5.51/kg
$11.03/kg
$5.64/kg
a One case of lettuce typically contains 24 heads of lettuce.
DISCUSSION
The current study suggests that Deep-Water
Culture system (DWC) and Nutrient Film
Technique (NFT) can be the good option
compared to Media-based Grow Bed (MGB)
as they can be intensified in commercial
settings. DWC, however, would not be a
good option for the location with limited
freshwater supply as this system requires a
large volume of water compared to other
systems. In terms of plant selection, herbs,
and specialty greens are highly suggested
(such as spinach, chives, basil, and
watercress) as they have low to medium
nutritional requirements and are well adapted
to aquaponics system (Diver 2006). On the
other side, tilapia is widely recommended
due to their adapting nature in the
commercial aquaponics system. Besides
these, the following technical challenges
should be addressed in order to transform this
aquaponics system from a small scale to a
commercial level (Sverdrup et al. 1981); (1)
improved nutrient solubilization and
recovery for a better use of the nutrient input
and reducing extra-mineral addition, e.g.,
phosphorus recycling; (2) adapted pest
management; (3) reduce water consumption
to a high degree by limiting the need for
water exchange; (4) use of alternative energy
sources for hot/cold and arid areas (e.g., CHP
(combined heat and power) waste heat,
geothermal heat, etc.); and (5) innovative pH
stabilization methods.
Journal of Agricultural, Environmental and Consumer Sciences - Vol. 19, 2019, 5-13
Given the overall sparseness of the economic
data and the inconstancy of the economic
profitability matrices used in the existing
literature, it is not possible to make a clear
conclusion on the aquaponics system at this
point. The same reason applies for NFT vs
DWC systems in terms of selecting the highly
profitable hydroponic bed for aquaponics
system. This was also agreed by Goddek et
al. (2015) in their review study on
aquaponics. Besides these, the hydroponic
unit for vegetables and other plants
production may be more profitable than the
fish production unit in aquaponics system.
This statement is matched with Bailey and
Ferrarezi (2017) argument and they stated
that recirculating aquaculture unit (under the
aquaponics system) was not profitable, but
crops like lettuce and basil grown in
aquaponics could be very profitable. Love et
al. (2014) however, in an international survey
of aquaponics growers, found a significant
relationship between sales of non-food
products from aquaponics farms and the
farms’ profitability. The authors suggested
that start-up aquaponics growers should
explore other alternative revenue sources
rather than depending solely on the
vegetables and fish items produced from the
aquaponics system to enhance economic
feasibility. Their survey also showed that
aquaponics located at USDA zones # 7‒13
(i.e., the research zones located in USA,
where the average annual extreme minimum
temperatures were maintained equal to or
above -17.77 °C or 0°F ) were more
profitable compared to USDA zone # 1-6
(i.e., the research zones, where the average
annual extreme minimum temperatures were
maintained below -17.77 °C or 0°F). This is
likely to be reduced risk of losses associated
with cold weather, power outages, and utility
costs. Thus, it is important to carefully assess
the economics of aquaponics system before
launching it in commercial level.
IMPLICATION
Given the fact that aquaponics follows
nutrient and water re-using principles, it
seems to be a promising solution for
sustainable recirculating aquaculture and
hydroponic practices. This is evidenced from
the experimental version (done mostly in
research settings) of this aquaponics system.
On the other side, very few studies have
endorsed that recirculating aquaculture unit is
a profitable enterprise under this aquaponics
system. In such situation, additional costs and
risks associated with this complex system
must be analyzed before investing the money
in adopting the aquaponics technique.
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