Title: Addressing the Conflation of Sandponics and the Integrated Aqua-Vegeculture System (IAVS) in Recent Literature
Authors: Barry Taylor
DOI: https://doi.org/10.5281/zenodo.17755470
Canonical Source:https://iavs.info/
Abstract
Precise nomenclature is essential for the advancement of integrated food production systems,
particularly within the fields of aquaponics and sustainable agriculture. This commentary
identifies and corrects a recurring terminological conflation in recent literature where the
Integrated Aqua-Vegeculture System (iAVs) is treated as synonymous with “Sandponics.”
Through a review of historical documentation and technical specifications, this paper
demonstrates that iAVs and Sandponics are distinct methodologies with separate origins,
operational principles, and input requirements. Specifically, iAVs is a biologically integrated
aquaculture-horticulture system developed at North Carolina State University in the 1980s,
relying on complex microbial processes to metabolize fish effluent for nutrition. Conversely,
Sandponics is a proprietary sand-culture system developed by Sumitomo Electric Industries
in the 1970s, dependent exclusively on chemical fertigation. The failure to distinguish
between these systems introduces significant methodological ambiguity, compromises the
reproducibility of data, and hinders the development of accurate protocols for food and water
security research
Full Text
- Introduction
The emerging field of integrated food production systems relies heavily on precise and
consistent nomenclature to ensure rigorous scientific comparison and technology transfer
(Colt et al., 2022; Palm et al., 2024). Adherence to standardized terminology is foundational
because it “ensures objectivity, clarity, and reproducibility” (Kretser et al., 2019).
Furthermore, accurate citation is not merely administrative; as Buchanan (2006) notes,
citation errors “diminish the usefulness of the data… and the validity of conclusions based on
those data,” effectively breaking the chain of evidence required for historical verification.
Ambiguity in terminology can lead to the misapplication of engineering principles and the
propagation of inaccurate design parameters. This commentary addresses the problematic
conflation of two distinct agricultural systems – Sandponics (SP) and the Integrated
Aqua-Vegeculture System (iAVs) – as observed in recent publications, notably Sewilam et al.
(2022), Nair et al. (2024), and Kimera et al. (2023; 2025).
Foundational literature illustrates that these two concepts originate from different historical
trajectories, feature distinct initial designs, serve unique purposes, and rely on varied
operational principles. The practice of equating them creates significant ambiguity,
potentially leading to misattributions of historical development and methodological errors. - The Conflation in Current Literature
Several recent studies explicitly define Sandponics as synonymous with the Integrated
Aqua-Vegeculture System. For instance, Sewilam et al. (2022) explicitly claim “sandponics
(SP), which is also referred to as an Integrated Aqua-Vegeculture system (IAVS),” a
statement also cited in Kimera et al. (2023). Similarly, Nair et al. (2024) assert that
“Sandponics, also known as the Integrated Aqua Vegeculture System (IAVS), presents a
promising solution.” Most recently, Kimera et al. (2025) refer to “Sandponics…also called
the integrated vegeculture-aquaculture system.”
This interchangeable usage obscures fundamental differences in the origins, primary
objectives, and technological configurations of the two systems. As analyzed in the following
sections, the literature establishes that these systems are mutually exclusive in their design
parameters. This conflation hinders replicable and comparative research. - Defining the Distinct Systems
The literature clearly establishes that these systems are mutually exclusive in their historical
origins, design parameters, and operational principles.
3.1. The Integrated Aqua-Vegeculture System (iAVs)
3.1.1. Historical Origins and System Overview
The Integrated Aqua-Vegeculture System (iAVs), developed and documented by Dr. Mark
McMurtry, Dr. Douglas C. Sanders, and colleagues at North Carolina State University
(NCSU) in the 1980s, is recognized as a foundational model for modern, sustainable
aquaponics (Diver, 2006; Abdelrahman, 2018; Goddek et al., 2019). It is a closed-loop,
integrated system that co-cultures fish and vegetables, designed to address waste
accumulation challenges in recirculating aquaculture.
The development team integrated distinct specializations to address the complex biological
interactions of the system, including horticulture and crop physiology (D.C. Sanders), plant
mineral nutrition (P.V. Nelson), aquaculture and zoology (R.G. Hodson), and International
Agricultural Development (H. Douglas Gross), agronomy (P.C. St. Amand), and plant
pathology (J.D. Cure). Between 1984 and 1994, the iAVs project was supported by a
comprehensive research consortium of 45 investigators and technical consultants. This
multidisciplinary group held advanced degrees across diverse fields, including botanical
mineral nutrition, aquatic veterinary medicine, soil genesis, agricultural economics, and
controlled environment engineering (including specialists from NASA and the Disney
EPCOT Land Pavilion).
3.1.2. Mechanical and Biological Filtration Processes
The empirical results detailed in the works of McMurtry et al. (1987–1997) offer specific,
quantifiable solutions and design parameters. In contrast to typical recirculating aquaculture
systems that remove solid waste prior to water reuse, the iAVs method pumps raw, unfiltered
fish tank effluent – containing both dissolved nutrients and suspended organic materials
(solids) – directly from the bottom of the fish tank onto sand biofilters composed of
medium-coarse sand (McMurtry et al., 1993a; 1993b; 1994; 1997a; 1997b). A specific
builder’s grade fractionation is used: predominantly Coarse (38.8%) and Very Coarse (33.3%)
inert sand, with minimal silt content (0.0% to <1% clay) and virtually zero fines (<200
microns) (McMurtry et al., 1997).
To facilitate the removal of these solids from the aquaculture component, the bottom is
sloped (e.g., 45°) to direct sediment toward the pump intake (McMurtry et al., 1997). These
sand beds serve a triple function: providing a physical substrate for plant roots, acting as a
medium for microbial nitrification, and facilitating the mechanical trapping and
mineralization of organic waste solids on the sand surface (McMurtry et al., 1993b).
Once pumped to the biofilter, water is distributed via shallow irrigation furrows. These
furrows act as sediment traps, slowing water velocity and allowing organic matter to settle on
the sand surface (McMurtry et al., 1993a). Empirical analysis confirms that this “furrow
effect” significantly increases Cation Exchange Capacity (CEC) and concentrates essential
elements within 50 mm of the furrow axis, providing a continuously renewed, localized
supply of solid-phase minerals to the root zone (McMurtry et al., 1990).
To ensure complete drainage and prevent waterlogging or anaerobic zones, the bottom of the
biofilter is constructed with a specific slope of 1:50 (2 cm drop per meter) toward the
drainage outlet (McMurtry et al., 1997). As the filtered water drains from the sand bed, it
cascades back into the fish tank, which re-oxygenates the water for the fish (McMurtry et al.,
1990).
The system operates on a “reciprocating” (flood and drain) cycle, typically irrigating 8 times
daily (McMurtry et al., 1997). Hybrid tilapia (Oreochromis mossambicus x O. niloticus) were
utilized due to their rapid growth, high market value potential, and hardiness in intensive
culture systems. The fish are fed at 08:00 (8 AM) and 13:00 (1 PM). The feed used in the
original trials was specifically not fortified with vitamins or trace elements to avoid potential
trace element toxicity (McMurtry et al., 1997).
3.1.3. Operational Parameters and Performance Attributes
The iAVs methodology exhibits specific operational characteristics regarding water chemistry
and system maintenance, as documented in technical assessments by Dr. H. Douglas Gross
(NCSU Department of Crop Science). Gross (1988) reported that iAVs facilities typically
develop into functionally mature ecosystems within three months from initial startup. The
longer the system is continuously operated without interruption or excess feed input rate, the
more stable it will tend to become biologically and chemically (Gross, 1988).
A primary feature is inherent pH stability; the system naturally maintains a pH between 6.0
and 6.5, which is an optimal range for nutrient availability to most plants. This stability
results from a biological balance where the acidifying process of nitrification is counteracted
by the base-releasing effects of mineralization and plant anion uptake, removing the
requirement for chemical pH adjusters often used in other hydroponic and aquaponic models
(McMurtry et al., 1990a; McMurtry et al., 1997a). This stability, however, is contingent upon
balancing nitrogen input with system assimilation (McMurtry 1990b). Therefore, operators
must strictly adhere to established design ratios regarding fish biomass and biofilter volume,
while regulating feed inputs to match metabolic demand (McMurtry 1990b; McMurtry et al.,
1997). Adherence to these protocols ensures the ecosystem remains within the specific 6.4
(±.4) pH range subsequently identified as critical for prioritizing soil ecology and plant
nutrient availability.
The system is designed for functional simplicity, allowing it to be operated by individuals
with “unsophisticated managerial skill” (McMurtry et al., 1997a). However, prior knowledge
of fish and plant care is beneficial for optimizing the biological balance of the system.
When sized correctly with medium-to-coarse sand (0.3-1.2 mm), the sand beds do not exhibit
clogging and do not require periodic cleaning or replacement. The design retains and
mineralizes organic solids within the sand bed, ensuring sequestered nutrients are available
for plant assimilation (McMurtry et al., 1993a). This integration of solids prevents nutrient
deficiencies often associated with solids removal in other systems (McMurtry et al., 1994;
Tyson 2011).
The ratio of plant growing area to fish volume is also critical. Specific biofilter-to-fish-tank
ratios (ranging from 0.67:1 to 2.25:1) were established through empirical trials. Studies
indicated that increased Biofilter Volume (BFV) resulted in improved water quality (lower
TAN and NO₂⁻ concentrations) and increased fish growth rates (McMurtry et al., 1997).
While vegetable yield per individual plant decreased with increasing BFV, the total fruit yield
per plot (total area) increased significantly, suggesting that larger biofilters maximize total
system biomass production (McMurtry et al., 1993b; McMurtry et al., 1997).
Extrapolation of annualized yield data by Professor Gross demonstrated that a unit with 3 m³
water and 14 m² biofilter area could yield ~150 kg fish and over 1000 kg of vegetables
annually, assuming a sub-tropical or controlled environment context (Gross, 1988; McMurtry
et al., 1997b). Gross (1988) further highlighted the system’s trophic efficiency, noting that
every 1.0 kg of feed input yields approximately 0.75 kg of fish and 6.70 kg of vegetables.
Fig. 1. Original schematic of the iAVs method. Reproduced from McMurtry et al., (1990)
with the purpose of critical comparison.
Fig. 2. Original schematic of the iAVs method. Reproduced from McMurtry et al., (1990)
with the purpose of critical comparison.
3.2. The Sandponics System
In contrast, “Sandponics” is a proprietary trademark of Sumitomo Electric Industries, Ltd.
(Baba & Ikeguchi, 2015; Kanazawa et al., 2017; Misu et al., 2018). Originally developed in
1977, it is a greenhouse-based system designed for year-round farming in a controlled
environment (Baba & Ikeguchi, 2015).
The key feature of the Sandponics system is its reliance on external chemical inputs. The
system uses a “Liquid fertilizer pump” and a “Liquid fertilizer Dilutor” to administer a
“Standard Sandponics fertilizer” containing inorganic salts (as shown in Figure 3) (Baba &
Ikeguchi, 2015; International Potato Center [CIP], 2019).
This system utilized an intermittent dripping irrigation method on air-permeable beds filled
with sand (Baba & Ikeguchi, 2015). Early challenges led to the development of the “New
Sandponics” (NSP) system in 2013, which transitioned to a floor irrigation method (as shown
in Figure 4) (Kanazawa et al., 2017). NSP utilizes capillary action via a specialized irrigation
cloth and root-proof sheets to draw nutrient solution upward from a bottom tank, a process
driven by soil moisture tension rather than gravity-fed dripping (Kanazawa et al., 2017). This
specific hydraulic configuration was designed to reduce the sand medium volume by 90%
compared to the original system and to enable precise control of liquid fertilizer supply based
on crop growth phases (Kanazawa et al., 2017).
Fig. 3. Configuration of the Sandponics System. Reproduced from Baba and Ikeguchi
(2015), with the purpose of critical comparison.
Fig. 4: Development of Sandponics devices. Reproduced from Kanazawa (2017), with the
purpose of critical comparison. - Clarifying the Evolutionary Timeline
Nair et al. (2024) suggest a linear evolution in which Sandponics served as a precursor to
iAVs. This assertion is not supported by the historical record. As detailed in Section 2, the
two systems followed parallel, yet distinct, developmental paths. The proprietary Sandponics
system has operated on chemical fertigation principles since its inception in 1977 through to
the “New Sandponics” update in 2013 (Baba & Ikeguchi, 2015; Kanazawa et al., 2017).
Conversely, iAVs was developed independently in the 1980s specifically as a biological
solution for aquaculture waste management (McMurtry et al., 1990a). There is no evidence in
the literature to suggest that the chemically-driven Japanese sand culture techniques were
adapted into the biological iAVs model. Consequently, the terms are not historically or
functionally interchangeable. - Implications of Terminology Conflation
The misattribution and conflation of these systems introduce methodological errors that
compromise the scientific value of reported studies. Furthermore, data derived from systems
incorrectly labeled as “Sandponics” (when they are actually iAVs) creates a false equivalence
in water use efficiency and yield metrics. This renders the data difficult to interpret or
replicate, effectively nullifying the utility of the research for those pursuing food and water
security solutions based on specific system constraints.
The root of this terminological confusion appears to lie in a reliance on non-peer-reviewed
information channels. Currently, for-profit operators such as Leedana ACG and
MyAquaponics market systems utilizing iAVs biological principles under the colloquial
‘Sandponics’ label (Leedana ACG, 2025; MyAquaponics, 2025). While marketing strategies
are the prerogative of private enterprise, their terminology must not be allowed to infect the
scientific record. When academic researchers draw from these informal sources without
tracing the historical primary literature, they risk legitimizing “self-promotion” as established
science. This creates what Jamieson et al. (2017) describe as a “polluted science
communication environment,” where informal usage degrades the ability of researchers to
“recognize valid science” (Redford, 2018), resulting in a literature base where distinct
methodologies are indistinguishable.
The conflation of terminology subsequently risks obscuring the distinct performance metrics
established for iAVs by McMurtry et al. By subsuming iAVs under the ambiguous label of
“Sandponics”, researchers risk producing data that fails to replicate these established
efficiency baselines. - Conclusion and Recommendations
The foundational principle for maintaining the integrity of the science record in integrated
food production systems is the necessity of rigorous methodology and precise, unambiguous
language (Gott 2019; Colt 2022). Accurate terminology and adherence to established
hydraulic and biological protocols are necessary to ensure the reproducibility of research. The
terms “Sandponics” and “iAVs” describe mutually exclusive methodologies: one is a
chemical fertigation system using sand, and the other is an integrated biological system
transforming aquaculture waste into plant biomass.
The conflation of a chemical method with a biological one is not merely a semantic error but
a categorical mistake that invalidates the theoretical basis of the affected studies.
Consequently, journals that have published papers equating Sandponics with iAVs – such as
those identified in this commentary – should consider issuing corrections or retractions to
prevent the further propagation of invalid design protocols. This situation underscores a
systemic lapse in the peer review process; proper scientific rigor requires reviewers to verify
historical precedents and technical specifications prior to publication.
This oversight risks normalizing “inadequate acknowledgement” – a recognized integrity
breach (Kretser et al., 2019) – and disseminates foundational errors that question the record’s
reliability (Casadevall et al., 2014; Hilgard & Jamieson, 2017). Peer review must therefore
guard against a “polluted” environment (Redford, 2018) by rejecting informal colloquialisms
that obscure technical distinctness. Future research must strictly distinguish between
(Sandponics) and the Integrated Aqua-Vegeculture System (iAVs) to facilitate the reliable
adoption of these technologies.
Competing Interests
The author serves as a volunteer administrator for iavs.info, a non-commercial educational
archive dedicated to preserving the historical scientific record of the Integrated
Aqua-Vegeculture System developed by Dr. Mark McMurtry. The preparation of this
commentary received no external financial support, and the analysis is based exclusively on a
review of peer-reviewed scientific literature. The author’s motivation for this commentary is
to ensure the integrity of the scientific record, thereby supporting researchers and
practitioners in their contributions to global food and water security.
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