Is Aquaponics Beneficial in Terms of Fish and Plant Growth and Water Quality in Comparison to Separate Recirculating Aquaculture and Hydroponic Systems?
Metadata
- Cite key: atiqueAquaponicsBeneficialTerms2022
- Item type: Journal Article
- Authors: F. Atique, P. Lindholm-Lehto, J. Pirhonen
- Affiliation: Department of Biological and Environmental Science, University of Jyväskylä, Finland (F.A., J.P.); Institute of Bioeconomy, JAMK University of Applied Sciences, Tarvaala, Finland (F.A.); Aquatic Production Systems, Natural Resources Institute Finland (Luke), Jyväskylä, Finland (P.L.-L.)
- Journal: Water 14 (2022) 1447
- Date: 04/2022
- Date added: [not reported]
- DOI: 10.3390/w14091447
- Funding: Maa- ja Vesitekniikan Tuki ry, Niemi-Foundation, and European Maritime and Fisheries Fund
- URL: https://doi.org/10.3390/w14091447
- PDF:
Atique et al. - 2022 - Is Aquaponics Beneficial in Terms of Fish and Plant Growth and Water Quality in Comparison to Separa.pdf
Opinion
A clean, well-designed three-arm comparison (coupled aquaponics vs. separate RAS vs. separate hydroponics, each n=3) that is unusually explicit about which arm is paired against which — exactly the “separate” comparator structure this vault’s extraction rules anticipate. The off-flavor (GSM/MIB) angle is a genuinely distinctive contribution not seen elsewhere in this batch. Let down by internal reporting slips: the FCR cell in Table 1 doesn’t match the number quoted twice in running text, and the nitrite peak values/days are told two different ways between Results and Discussion in a pattern that looks like the two treatments’ numbers got swapped. Neither is fatal to the paper’s headline conclusions (fish grew better in aquaponics; spinach grew equally well in both soilless systems), but both need checking against the underlying data before citing exact figures.
Abstract
Aquaponics is a technique where a recirculating aquaculture system (RAS) and hydroponics are integrated to grow plants and fish in a closed system. We investigated if the growth of rainbow trout (Oncorhynchus mykiss) and baby spinach (Spinacia oleracea) would be affected in a coupled aquaponic system compared to the growth of the fish in RAS or plants in a hydroponic system, all systems as three replicates. We also investigated the possible effects of plants on the onset of nitrification in biofilters and on the concentration of off-flavor-causing agents geosmin (GSM) and 2-methylisoborneol (MIB) in rainbow trout flesh and spinach. For the fish grown in aquaponics, the weight gain and specific growth rates were higher, and the feed conversion ratio was lower than those grown in RAS. In spinach, there were no significant differences in growth between aquaponic and hydroponic treatments. The concentration of GSM was significantly higher in the roots and MIB in the shoots of spinach grown in aquaponics than in hydroponics. In fish, the concentrations of MIB did not differ, but the concentrations of GSM were lower in aquaponics than in RAS. The onset of nitrification was faster in the aquaponic system than in RAS. In conclusion, spinach grew equally well in aquaponics and hydroponic systems. However, the aquaponic system was better than RAS in terms of onset of nitrification, fish growth, and lower concentrations of GSM in fish flesh.
Summary
The authors ran a 42-day, fully replicated (n=3 per arm) side-by-side comparison of a coupled aquaponic system (rainbow trout + baby spinach sharing one recirculating loop) against a separate RAS (fish only) and a separate hydroponic system (spinach only, Substral nutrient solution), all housed in the same unheated industrial hall in Finland. Beyond standard growth and water-quality metrics, the study’s distinctive angle is off-flavor chemistry: it tracked geosmin (GSM) and 2-methylisoborneol (MIB) — compounds responsible for musty/earthy taint — in water, fish muscle, and spinach tissue, and tracked the onset of nitrification (TAN → nitrite → nitrate) to test whether plants speed up biofilter start-up. Fish in aquaponics grew significantly faster and more efficiently than fish in RAS (higher SGR and weight gain, lower FCR), which the authors attribute to better water quality (faster nitrification onset, lower steady-state nitrate) rather than to feed differences, since feed intake was statistically identical between the two fish arms. Spinach grew statistically the same in aquaponics and hydroponics by dry weight, though aquaponic spinach trended ~43% heavier and had a distinctly different mineral profile (more Fe/Zn/B/Ca/Mg, less N/P/K/S, tied to the different micronutrient supplementation and RAS-derived nutrients versus the manufactured Substral solution). GSM was lower in aquaponic fish flesh than RAS fish flesh, but MIB in flesh and both compounds in water did not differ meaningfully between the fish-side treatments; on the plant side, GSM was higher in aquaponic spinach roots and MIB higher in aquaponic spinach shoots than in hydroponic spinach. Practically, this is one of the more direct pieces of evidence in the literature that plants in a coupled loop can measurably improve fish welfare/growth outcomes relative to a standalone RAS, at least for rainbow trout and under a short (six-week) start-up-phase trial.
Experiment data
- Location: Tarvaala Bioeconomy campus, JAMK University of Applied Sciences, Finland; industrial hall, no temperature control
- Design: Three-arm comparison, each replicated n=3 (3 RAS + 3 aquaponic + 3 hydroponic systems), 42 days (4 May–14 June 2021)
- Replicates / n: 3 systems per treatment; observational unit = tank or tray (n=3) throughout
- Duration: 42 days
- Organisms: Rainbow trout (Oncorhynchus mykiss) / Spinach (Spinacia oleracea), baby spinach cultivar not specified
- Statistics: Independent-samples t-test (growth, minerals, lipid, off-flavor treatment comparisons); repeated-measures ANOVA with Greenhouse-Geisser or Huynh-Feldt adjustment (time-course water quality, anions, off-flavors); one-sample t-test (start vs end); Levene’s test; IBM SPSS Statistics 26
- Specific Growth Rate (SGR): aquaponics 1.95 ± 0.12 %/day vs RAS 1.67 ± 0.08 %/day (p<0.05)
- Feed Conversion Rate (FCR): aquaponics 0.85 ± 0.08 vs RAS 1.06 ± 0.03 (p<0.05) — ⚠️ see Extraction notes, Table 1 itself prints 0.86
- Nitrate (NO3): aquaponics 12.30 ± 0.83 mg/L vs RAS 26.98 ± 1.04 mg/L (overall trial level, Discussion)
- Plant total dry weight: aquaponics 1.53 ± 0.48 g/plant vs hydroponics 1.07 ± 0.29 g/plant (ns)
Fish growth and feed conversion
This paper: Rainbow trout grown in the coupled aquaponic system had significantly higher weight gain (137.1 ± 11.29 g vs 109.3 ± 3.05 g), higher SGR (1.95 ± 0.12 vs 1.67 ± 0.08 %/day), and lower FCR (0.85 ± 0.08 vs 1.06 ± 0.03) than fish grown in separate RAS, despite statistically identical feed intake per fish (110.0 vs 112.0 g/fish, ns). No mortality occurred in aquaponics; one fish died in one of the three RAS tanks. The authors attribute the fish-growth advantage to better water quality in the aquaponic loop (faster nitrification onset, lower steady-state nitrate) rather than to feed differences.
Compared with:
- todo Pulkkinen et al. 2019 — reported RAS-grown rainbow trout SGR of 1.58 ± 0.03 for similar size/temperature, used by the authors as a benchmark that both of their own systems (1.67 and 1.95) show good growth. (p. 9)
- todo Davidson et al. 2014 — found no FCR/weight difference between rainbow trout at “low” (30 mg/L) vs “high” (91 mg/L) nitrate in RAS, but final biomass/density were higher at low nitrate; FCR was ~1.3 in both, higher than either arm in this study. (p. 9)
- todo Lennard and Leonard 2006 — FCR of 0.85 reported for Murray cod in aquaponics, matching this paper’s aquaponic FCR. (p. 9)
- todo Palm et al. 2015 — FCR of 0.93 reported for Nile tilapia in aquaponics. (p. 9)
Onset of nitrification
This paper: TAN, nitrite, and pH differed significantly between treatments and over time (all p<0.0001 except TAN, which varied over time but not by treatment). TAN fell below 1 mg/L by day 9 in aquaponics vs day 11 in RAS. Nitrite reached near-zero by day 11 in aquaponics; the same point took substantially longer in RAS (39 days per Results, 34 days per Discussion — ⚠️ see Extraction notes). Peak nitrite concentration was ~4.83 mg/L in both treatments but the SD and exact RAS peak day are internally inconsistent between Results and Discussion (⚠️BLOCK, see Extraction notes). Nitrate stayed lower in aquaponics than RAS through most of the trial (peaking 81.67 ± 2.88 mg/L day 9 in aquaponics vs ~80 mg/L day 14 in RAS), converging near day 42; the paper’s own “overall level” summary gives 12.30 ± 0.83 mg/L (aquaponics) vs 26.98 ± 1.04 mg/L (RAS).
Compared with:
- todo Fischer et al. 2021 — comparable RAS-vs-aquaponics study (largemouth bass, spring onion, lemongrass) found no TAN/nitrite/pH difference between treatments but nitrate higher in RAS throughout, similar directional pattern to this paper’s nitrate result; also found Streptomyces present in RAS but absent in aquaponics, and greater bacterial diversity in aquaponics. (p. 11, 13–14)
- todo Timmons et al. 2018 — cited for acceptable TAN/nitrite thresholds (<1 mg/L, preferably ~0) and general RAS alkalinity-management practice. (p. 10–11)
Spinach growth and mineral composition
This paper: No significant difference in shoot, root, or total dry weight, shoot:root ratio, or shoot/root length between aquaponic and hydroponic spinach (Table 2), though total plant weight trended 43% higher in aquaponics (not stated as significant). Macronutrients N, P, S, K were significantly higher in hydroponic spinach (attributed to the manufactured Substral solution’s known composition); Ca and Mg were significantly higher in aquaponic spinach (attributed to fish feed content). Micronutrients Fe, Zn, and B were significantly higher in aquaponic spinach (attributed to the added Fe/Mn/Zn/Mo/K micronutrient solution); Cu and Mn did not differ.
Compared with:
- todo Maneejantra et al. 2016 — macronutrient concentrations in spinach shoots broadly comparable to this study, except Mg was lower in their hydroponic spinach and Ca higher in their aquaponic spinach (opposite pattern noted by the authors as a discrepancy worth follow-up). (p. 12)
- todo El-Sayed 2020 — reported iron concentration of 267 mg/kg in market spinach, lower than the 523.3 mg/kg found here in aquaponic spinach. (p. 12)
- todo Pantanella et al. 2012 and Delaide et al. 2016 — cited as supporting evidence that aquaponics can match or exceed hydroponic yield, consistent with this paper’s non-significant yield difference. (p. 13)
Off-flavors (geosmin and MIB)
This paper: GSM in fish muscle was significantly lower in aquaponics than RAS (376.0 ± 24.99 vs 466.3 ± 39.40 ng/kg at end); MIB in muscle did not differ between fish treatments. Neither GSM nor MIB differed significantly between aquaponics and RAS in water (DWC or fish-tank compartments). In spinach tissue, GSM was significantly higher in aquaponic roots than hydroponic roots, and MIB was significantly higher in aquaponic shoots than hydroponic shoots (Table 7) — this is the paper’s most novel finding, since it demonstrates off-flavor compounds can be taken up into edible plant tissue in a coupled system, at levels the authors argue remain below or near typical sensory-detection thresholds for GSM but above them for MIB.
Compared with:
- todo Howgate 2004 — review cited for GSM/MIB uptake kinetics and sensory detection thresholds (700–900 ng/kg) used throughout the Discussion. (p. 13)
- todo Maher and Goldman 2017 — reported much higher GSM concentrations in beet (43,000–17,300 ng/kg) than found in this study’s spinach. (p. 14) [secondary, cites original beet-breeding study]
- todo Suurnäkki et al. 2020 and Burr et al. 2012 — cited as typical RAS GSM/MIB water-concentration ranges (5–25 ng/L GSM, 50–130 ng/L MIB), broadly consistent with this study’s own measured range (2–8 ng/L GSM, 13–36 ng/L MIB). (p. 13)
Linked claims
- Aquaponic fish can outgrow RAS-only fish under matched feed intake
- Plants in a coupled aquaponic loop speed up biofilter nitrification onset relative to fish-only RAS
- Off-flavor compounds (GSM, MIB) can accumulate in edible plant tissue in a coupled aquaponic system
- Spinach grows equivalently in aquaponics and hydroponics despite different nutrient sources
Citations to chase
- todo Pulkkinen et al. 2019 — RAS-grown rainbow trout SGR benchmark (1.58 ± 0.03)
- todo Davidson et al. 2014 — nitrate tolerance thresholds in RAS-reared rainbow trout
- todo Lennard and Leonard 2006 — Murray cod FCR (0.85) in aquaponics, comparator value
- todo Palm et al. 2015 — Nile tilapia FCR (0.93) in aquaponics, comparator value
- todo Fischer et al. 2021 — closest comparable RAS-vs-aquaponics study design (largemouth bass, spring onion, lemongrass); also source of the bacterial-community comparison (Streptomyces present in RAS, absent in aquaponics)
- todo Maneejantra et al. 2016 — spinach hydroponic nutrient-requirement study used for mineral-content comparison
- todo El-Sayed 2020 — market spinach iron content comparator
- todo Howgate 2004 — GSM/MIB uptake and sensory-threshold review
- todo Maher and Goldman 2017 — GSM in beet, secondary figure
- todo Suurnäkki et al. 2020 — RAS off-flavor water-concentration ranges
Extraction notes
⚠️BLOCK NO2-N (misattribution pattern): Results (p.6): “The highest mean nitrite concentrations were recorded (4.83 ± 0.28 mg/L, n = 3) in aquaponics on day 7 but on day 11 in RAS treatment.” Discussion (p.10–11): “the peak concentration of nitrite (4.83 ± 0.14 mg/L) in aquaponics was reached on day 7, while it took 11 days longer in RAS (4.83 ± 0.28 mg/L).” The SD attached to the aquaponics peak differs between passages (0.28 vs 0.14), and the 0.28 value Results attaches to aquaponics is exactly what Discussion attaches to RAS instead. The RAS peak day also conflicts (day 11 in Results vs day 18 implied by “11 days longer” in Discussion), and RAS’s near-zero-nitrite day conflicts (39 days in Results vs 34 days in Discussion). Not reconcilable from the text. NO2-N recorded UNCLEAR in trials.csv. Treated as misattribution per SCHEMA.md → contributes to quality: suspect.
⚠️MATERIAL FCR: Table 1 (p.6) prints aquaponics FCR as 0.86 ± 0.08, but both Results (p.6) and Discussion (p.9) state 0.85 ± 0.08 in running text, referencing Table 1. The two independent textual mentions were taken as the recorded value (0.85 ± 0.08); Table 1’s own printed digit (0.86) is the likely typo/rounding slip, noted in trials.csv remarks.
⚠️CHECK NO3-N (different definitions): Discussion’s “overall level of nitrate” (12.30 ± 0.83 mg/L aquaponics / 26.98 ± 1.04 mg/L RAS, full-trial colorimetric mean) does not match the day-42-only ion-chromatography anion panels in Table 4 (DWC: 3.44 ± 1.96 vs 4.51 ± 2.74) or Table 5 (fish tank: 4.11 ± 1.16 vs 2.00 ± 1.08). These are different analytes/methods/timepoints, not a genuine conflict; recorded the “overall level” figure as the clearest basis for a trial mean, all three kept in remarks.
⚠️CHECK Table 7 unit: table header states “ng/L” for spinach tissue GSM/MIB, but Methods 2.3 defines solid-sample LOQs in ng/kg and Table 6 uses ng/kg for muscle (also solid tissue) — almost certainly a copy-paste header error. Recorded as ng/kg in plant_measurements.csv with this caveat.
⚠️MINOR Days Plant after transplant: transplant (5 May) to harvest (14–15 June) spans 40–41 calendar days, but the paper consistently and repeatedly states “42-day experiment” for both fish and plant throughout (Abstract, Methods, all table captions). Recorded 42 per the paper’s own repeated statement.
⚠️MINOR Table 7 caption states a blanket “n=3, means ± SD” but the printed Start-column values carry no SD at all; Methods 2.2 indicates Start and End sampling used different numbers of plants (six seedlings vs three plants per tray). Start values recorded as printed (SD = NR).
[not reported] / [unclear] grouped by field: Initial Stock density, Fish Category, Plant Category, Water classification, pHOptimal, FUE AP, FUE HYD, WUE, EC, SPAD, Leaf count, Plant fresh weight, Plants/m2, Lat, Long, Tissue nitrate AP, Tissue nitrate HYD, Total Feed (kg), Fish biomass created (kg), Water recycle, Water volume in the system, Remineralization — none of these are stated anywhere in the paper, or (for Plants/m2, Total Feed, Fish biomass created, Water volume) would require combining separately-stated numbers, which is derivation and therefore excluded per the prime directive.
Water quality reported as time series/ranges rather than single trial means for: Aq pH, Water temperature, TAN/NH4-N, Average room Temperature — recorded as ranges with “no trial mean reported” per SCHEMA.md’s range-only rule. Dissolved Oxygen reported only as % saturation (80–85%), not ppm; not converted since %-saturation → ppm requires temperature/pressure assumptions beyond the permitted exact unit-conversion rule, so recorded NR with the % figure noted in remarks.
NO COLUMN items (see Experimental Remarks in trials.csv for full detail): fish muscle lipid content; off-flavor GSM/MIB in water and fish muscle (Table 6 — no column exists anywhere in the 87-column schema for this analyte; see report on excluded water/fish panel); anion panel chloride/phosphate/sulfate (Tables 4–5, and tap-water baseline); feed fat content (51%); spinach shoot/root length and shoot:root ratios; spinach shoot/root weight breakdown (only the combined total was routed to the AP/HYD columns).
Judgment call: AP/HYD columns were used for total per-plant dry weight (1.53 ± 0.48 g aquaponics vs 1.07 ± 0.29 g hydroponics, Table 2) rather than the “Plant dry matter” column, since the paper reports only raw dry weight (no % dry matter) and this is the closest analogue to this vault’s existing yield-comparison precedent (alcarrazQualityLettuceLactuca2018). “Plant dry matter” and “Plant fresh weight” left NR to avoid duplicating the same number in two homes.
Tag note: Region tagged Europe (continent-level, matching the granularity of existing South-America-tagged notes in this vault); Country = Finland. No coordinates given anywhere in the paper, so Lat/Long = NR rather than looked up externally.
Source: Atique et al. - 2022 - Is Aquaponics Beneficial in Terms of Fish and Plant Growth and Water Quality in Comparison to Separa.pdf
Data Tables
Structured data extracted from this paper into the vault's
trials.csv/plant_measurements.csvdatasets. Fields the paper didn't report are omitted. Download the full datasets (measurements).
Trial Parameters
atiqueAquaponicsBeneficialTerms2022-T1
Fish
| Field | Value |
|---|---|
| Fish | Rainbow trout (Oncorhynchus mykiss) |
| FCR | 0.85 +/- 0.08 |
| SGR | 1.95 +/- 0.12 |
| Protein | 43 |
| Fish size initial | 108.2 +/- 1.26 |
| Fish size final | 245.3 +/- 10.32 |
| Feed routine | Fed by hand twice per day for the first week, then with automatic feeders three times per day |
| Feed regime | Dry pellets (EFICO Enviro 923 Advance 4.5 mm, Biomar, Brande, Denmark); crude protein 43%, fat 51% per manufacturer; daily ration adjusted based on uneaten feed (siphoned, counted, converted using 14 dry pellets = 1.00 g) |
| Fish survival rate | 100% (no mortality reported) |
| Fish weight gain | 137.1 +/- 11.29 |
| Fish trial duration (days) | 42 |
Water
| Field | Value |
|---|---|
| Water type | Tap water |
| Daily Water exchange rate | 10-50% (varies by week: wk1 50% x4, wk2 20-30% x4, wk3-4 10% x3, wk5 0%, wk6 20-30% x2; range only, no single daily rate reported) |
| Aq pH | 7.76 to 6.83 (range; gradual decline over 42 d, no single trial mean reported) |
| Dissolved Oxigen | NR (reported as 80-85% O2 saturation, not ppm; see remarks) |
| Water temperature | 12 to 19 (range; no trial mean reported) |
| TAN / NH4-N | NR (time series only; see remarks) |
| NO2-N | UNCLEAR (see remarks - WARN-BLOCK) |
| NO3-N | 12.30 +/- 0.83 |
Plant
| Field | Value |
|---|---|
| Plant | Spinach (Spinacia oleracea), baby |
| Details | Transplanted 5 May 2021 as seedlings pre-grown 3 weeks in a greenhouse; harvested 14-15 June 2021 (end of the 42-day experiment); 20 plants sampled per DWC at harvest |
| Days Plant after transplant | 42 |
System & Setup
| Field | Value |
|---|---|
| System type | Deep water culture (DWC) |
| Media Details | DWC tanks (W1 x L1 x D0.35 m), high-density polyethylene containers; rafts of extruded polystyrene foam (XPS) Styrodur with 25 drilled holes for 5 cm hydroponic pots filled with expanded clay; continuously aerated via air stones; LED lighting (Kinwua Bright, 215 W, ~1000 lux) 16 h/day |
| Biological system already in use | N (Biofilters were newly started, not a pre-established system: 250 mL filter starter (Easystart) added to each biofilter tank one week before (27 April) and six days after (10 May) fish stocking (4 May); study explicitly investigates the onset of nitrification) |
| Air supplement | Y (DWC continuously aerated via air stones; fish tanks aerated via air pumps/air stones maintaining 80-85% O2 saturation throughout) |
| Iron supplemented | Y (Modified micronutrient solution (Fe, B, Zn, Mo) plus K added to the aquaponic system: Fe(NO3)3.9H2O 101.2 g, Mn(NO3)2.4H2O 36.52 g, Zn(NO3)2.6H2O 2.7368 g, Na2MoO4.2H2O 0.3533 g, K2B4O7.4H2O 28.26 g dissolved in 1 L water; 10-15 mL added whenever water was added to the system or plants showed deficiency symptoms; plants also sprayed daily (1 mL solution in 1.5 L water) excluding week 1) |
| pH Buffers | N (No chemical pH buffer used in either treatment during the trial; RAS pH drop after day 30 attributed to ‘the lack of alkalinity management’ (p.11); aquaponics pH stability attributed to passive plant nutrient uptake/root H+/OH- exchange, not an added buffer (p.11)) |
| Climate control | N (Industrial hall without temperature control (Methods 2.1, p.3); water temperature rose uncontrolled from 12 to 19 degC over the 42-day experiment) |
| Artificial Lighting | Y (LED lights (Kinwua Bright, 215 W, light intensity c. 1000 lux) provided to plants 16 h/day; scattering light from the DWCs also illuminated the fish tanks, which had no separate lamps) |
| Nutrient supplemented | Y (Aquaponic plants received the Fe/Mn/Zn/Mo/K micronutrient solution described above (see Iron supplemented) in addition to nutrients from the RAS effluent. Paired hydroponic control instead received Substral (Transmeri) nutrient solution: 408 mL Substral per 350 L water added every two weeks to compensate evaporation, plus daily spray of ~1 mL Substral in 1.5 L water (excluding week 1); manufacturer-stated composition N 6%, P 1.3%, K 5%, S 0.6%, Cl <0.5%) |
| Equipment | GC-QQQ (7000 Series Triple Quadrupole MS, Agilent) with Phenomenex Zebron ZB-5MSi column and PAL3 autosampler (GSM/MIB); Dionex Integrion HPIC ion chromatograph (anions); Foss Soxtec/Hydrotec 8000 (fish muscle lipid, AOAC 920.39/954.02, AACC 30-25); Digital pH/Temp Meter AD12 (ADWA); ExStik DO600 dissolved oxygen meter (Extech); API Freshwater master test kits (TAN, nitrite, nitrate); humidity meter (Prego); bead filter (SuperBead small, 37.5 kg beads) + moving bed biofilter (300 L helix media) + UV light (AquaForte UV-C 18 W) per fish-tank loop |
| Control Parameters | 3+3+3 replicated RAS / aquaponic / hydroponic systems (n=3 each); O2 saturation held at 80-85% via air pumps/air stones; scheduled weekly water exchange (see Daily Water exchange rate remarks); feed ration adjusted daily from uneaten-pellet counts; water quality recorded daily in week 1, then 3-4x/week; fish not fed on harvest day |
| Combination | Rainbow trout and baby spinach; coupled aquaponics (fish+plant, shared loop) vs. separate RAS (fish only) and separate hydroponics (plant only) controls, 42-day trial |
Site
| Field | Value |
|---|---|
| Region | Europe |
| Country | Finland |
| Average room Temperature | 15 to 20 (range; DWC air temperature, no single trial mean reported) |
Results & Statistics
| Field | Value |
|---|---|
| Measured Unit | g dry wt/plant (total plant weight, Table 2); g/kg or mg/kg DM (leaf minerals, Table 3); ng/L (GSM/MIB in water, Table 6); ng/kg (GSM/MIB in fish muscle, Table 6); ng/L as printed / ng/kg as likely intended (GSM/MIB in spinach tissue, Table 7 - see remarks) |
| Statistic Details | Independent-samples t-test (fish growth, plant biomass, macro/micronutrients, muscle lipid, off-flavors between treatments); repeated measures ANOVA with Greenhouse-Geisser (TAN/nitrite/nitrate/pH over time) or Huynh-Feldt adjustment (anions, GSM/MIB); one-sample t-test (start vs end values); Levene’s test for homogeneity of variance; IBM SPSS Statistics 26 |
| Statistically analysed | Y |
| Replicates (n) | 3 |
| AP | 1.53 +/- 0.48 |
| HYD | 1.07 +/- 0.29 |
Experimental Remarks: TRIAL DEFINITION: T1 = the coupled aquaponic treatment (rainbow trout + baby spinach sharing one recirculating loop, DWC water pumped back to the fish tank). Paired controls: separate RAS (fish-only, no plants) for all fish-side comparisons; separate hydroponics (plant-only, Substral nutrient solution) for all plant-side comparisons. Both controls run as 3 replicate systems in parallel with 3 replicate aquaponic systems (3+3+3 design). Only one aquaponic treatment in this paper, so one row. RAS/HYD comparison values have no dedicated columns in this schema outside AP/HYD (used here for total plant dry weight) and Tissue nitrate AP/HYD (NR, not measured); all other RAS/HYD figures are recorded below in remarks. | WARN-BLOCK NO2-N (misattribution pattern): Results (p.6, Sec 3.3): ‘The highest mean nitrite concentrations were recorded (4.83 +/- 0.28 mg/L, n = 3) in aquaponics on day 7 but on day 11 in RAS treatment.’ Discussion (p.10-11, Sec 4): ‘the peak concentration of nitrite (4.83 +/- 0.14 mg/L) in aquaponics was reached on day 7, while it took 11 days longer in RAS (4.83 +/- 0.28 mg/L).’ The SD attached to the AQUAPONICS peak differs between the two passages (0.28 vs 0.14), and the 0.28 value Results attaches to aquaponics is the same value Discussion attaches to RAS instead — consistent with the two arms’ SDs having been swapped between passages. Compounding this: ‘day 11’ for the RAS peak (Results) does not match ‘day 7 + 11 days longer’ = day 18 (Discussion); and Results separately states RAS reaches near-zero nitrite in 39 days vs Discussion’s 34 days. Not reconcilable from the text; cannot tell which SD/day belongs to which treatment. NO2-N (aquaponics) recorded UNCLEAR. Affects: NO2-N cell; any fine-grained comparative nitrite-onset timing claim (the coarser TAN and nitrate onset-timing claims are sourced from passages that do not show this conflict and are unaffected). Quality impact: treated as misattribution per SCHEMA.md, hence BLOCK and quality:suspect. | WARN-MATERIAL FCR: Results (p.6, Sec 3.1): ‘The FCR in aquaponics was significantly lower (0.85 +/- 0.08) than in RAS (1.06 +/- 0.03) (Table 1).’ Discussion (p.9, Sec 4): ‘The feed conversion ratio of rainbow trout in the aquaponic system was lower (0.85 +/- 0.08) than in RAS (1.06 +/- 0.03).’ Table 1 itself (p.6) prints ‘FCR 1.06 +/-0.03 [RAS] 0.86 +/-0.08 [Aquaponics]’. Two independent textual restatements (Results, Discussion) agree on 0.85 +/- 0.08 for aquaponics; only Table 1’s own printed digit differs (0.86), by 0.01 — likely a rounding/typo in the table cell. Recorded 0.85 +/- 0.08 (majority/consistent value); Table 1’s 0.86 is the outlier, noted here. RAS FCR (1.06 +/- 0.03) is identical across all three mentions — no issue there. Recompute check only (not entered in any cell): per-fish feed/gain from Table 1, 110.0/137.1 = 0.80, does not exactly reproduce either 0.85 or 0.86 — consistent with FCR being calculated per-tank then averaged rather than from pooled means; this check is inconclusive and does not itself resolve which of 0.85/0.86 is correct. | WARN-CHECK NO3-N (different definitions/methods): Discussion (p.9): ‘the overall level of nitrate was lower in the aquaponics treatment (12.30 +/- 0.83) than in RAS (26.98 +/- 1.04)’ — reads as a genuine full-trial mean (API colorimetric test-kit method used throughout the 42-day course per Methods 2.6). Table 4 (p.8, end-of-experiment ion-chromatography anion panel, DWC compartment): Nitrate-N aquaponics = 3.44 +/- 1.96 mg/L, hydroponics = 4.51 +/- 2.74 mg/L (day 42 only). Table 5 (p.9, end-of-experiment anion panel, fish-tank compartment): Nitrate aquaponics = 4.11 +/- 1.16 mg/L, RAS = 2.00 +/- 1.08 mg/L (day 42 only). These do not contradict the Discussion figure under a BLOCK reading — they are a different analyte definition (single day-42 ion-chromatography snapshot vs full-trial colorimetric mean) and the paper never states which is ‘the’ nitrate figure. Recorded NO3-N = 12.30 +/- 0.83 mg/L (clearest basis: explicitly labelled ‘the overall level’, matches the schema’s trial-mean definition). All three candidates (12.30+/-0.83 ‘overall’; 3.44+/-1.96 DWC day-42; 4.11+/-1.16 fish-tank day-42) kept here for the user to judge which definition their analysis needs. | WARN-CHECK Table 7 unit (ng/L vs ng/kg for spinach tissue GSM/MIB): Table 7 header (p.10) literally states ‘Concentrations (ng/L) of off-flavors … in spinach’; but Methods 2.3 (p.5) defines solid-sample LOQs in ng/kg (‘65 ng/kg GSM; 107 ng/kg MIB … for solid samples’), and Table 6’s own header correctly separates water (ng/L) from muscle (ng/kg, a solid tissue). Spinach shoot/root tissue is a solid sample like muscle, so ng/L is physically implausible and very likely a copy-paste header error from the water tables. Recorded as ng/kg in plant_measurements.csv with this caveat; numeric magnitudes are unaffected and recorded as printed. Added to REVIEW.md scope for user confirmation. | WARN-MINOR Days Plant after transplant: transplant dated 5 May; harvest dated 14-15 June -> calendar span of 40-41 days, not 42. However ‘42-day experiment’/‘for 42 days’ is stated repeatedly and consistently for both fish and plant (Abstract, Methods 2.1, Table 1/2/3 captions, Fig.1 caption). Recorded 42 per the paper’s own consistent repeated statement; the 1-2 day arithmetic discrepancy is noted for verification only, since (unlike FCR/nitrite above) no alternative duration number ever appears anywhere in the paper. | WARN-MINOR Table 7 n/SD inconsistency: Table 7’s caption states ‘Values are means +/- SD, n = 3’ uniformly, but the printed Start-column values (1079.4, 1260.6, 134.4, 212.8 ng) carry no +/- SD at all, inconsistent with a blanket n=3+SD claim; Methods 2.2 states six spinach seedlings were sampled at the start per tray vs three at the end, so Start and End likely do not share n=3 despite the caption. Start values recorded exactly as printed (SD = NR); does not affect any End-value cell. | NOT DERIVED, left NR: Initial Stock density (20 fish of c. 90-110 g in a 500 L tank — fish count and tank volume given, not stated as kg/m3); Total Feed kg (only per-fish feed consumed given: 110.0+/-0.01 g/fish AP vs 112.0+/-0.03 g/fish RAS, Table 1 — multiplying by fish count/tank would be derivation); Fish biomass created kg (only per-fish weight gain given, 137.1+/-11.29 g/fish — multiplying by fish count would be derivation); Water volume in the system (fish tank 500 L + settling tank 500 L + DWC 350 L given separately in Methods 2.1 — summing would be derivation); Plants/m2 (DWC raft W1 x L1 m with 25 planting holes given separately, Methods 2.1 — computing density would be derivation). | Water quality reported mostly as time series/ranges, not single trial means (per SCHEMA.md range-only rule): Aq pH varied 7.76+/-0.05 (start) to 6.83+/-0.05 (end), gradual decline (Fig.1d, p.7) — range only. Water temperature rose uncontrolled from 12 to 19 degC over the trial (Methods 2.1, p.3) — range only. TAN peaked at 2.00+/-0.00 mg/L on day 6, near-zero by day 11 (Fig.1a/Results 3.3, p.6-7) — range only, no trial mean stated. Dissolved Oxygen reported only as % saturation maintained at 80-85% (Methods 2.1, p.3), not ppm — recorded NR because %-saturation to ppm is not a safe exact unit conversion (depends on temperature/pressure), so it is not permitted under the ‘unit conversion only’ rule; 80-85% saturation noted here instead (NO COLUMN). Average room Temperature: DWC air temperature ranged 15-20 degC (Methods 2.1, p.3) — range only. | NO COLUMN: Fish muscle lipid content (6.0% at start -> 7.5+/-0.9% RAS, 6.3+/-1.7% aquaponics at end, ns, p.9-10) — no lipid-content column for fish tissue. Off-flavor GSM/MIB in water (DWC and fish-tank compartments, Table 6, ng/L) and in fish muscle (Table 6, ng/kg) — no GSM/MIB column exists anywhere in this 87-column schema; EXCLUDED from trials.csv entirely for this reason (flagged in the batch report as a water/fish panel with no home). Anion panel chloride/phosphate/sulfate (Tables 4 and 5, mg/L, aquaponics vs hydroponics vs RAS) — no columns exist for these analytes (only NO3-N has a column); tap-water baseline also given (7.7 mg/L Cl-, 0.21 mg/L NO3-N, 0.75 mg/L SO4 2-, p.7) with no home. Feed fat content (51%, Methods 2.1, p.3) — no ‘Fat’ column alongside Protein/N/P/K; flagged for verification as an unusually high value for a fish feed but not internally contradicted elsewhere in the paper, so not given a formal severity tag. Shoot/root length and shoot:root ratios (Table 2, p.7: shoot length AP 14.50+/-1.69 vs HYD 12.15+/-1.32 cm; root length AP 37.77+/-5.73 vs HYD 29.23+/-4.63 cm; shoot:root ratio weight AP 4.50+/-1.46 vs HYD 5.54+/-2.77; shoot:root ratio length AP 0.40+/-0.03 vs HYD 0.44+/-0.02) — not routed to ‘Plant height’ per existing vault precedent (shoot length is not whole-plant height; cf. lenzCommonChicoryProduction2021’s LLL exclusion). Shoot weight and root weight separately (Table 2: shoot AP 1.23+/-0.34 vs HYD 0.88+/-0.27 g; root AP 0.30+/-0.16 vs HYD 0.18+/-0.08 g) — only the combined total weight was routed to the AP/HYD columns; the shoot/root breakdown has no separate home. | AP/HYD columns hold total per-plant dry weight (g/plant, Table 2, p.7) rather than the ‘Plant dry matter’ column, since the paper reports only raw dry weight (no %DM) and this is the closest analogue to the worked yield-comparison precedent (alcarrazQualityLettuceLactuca2018’s AP/HYD = g fw/m2 yield); ‘Plant dry matter’ and ‘Plant fresh weight’ left NR to avoid duplicating the same number in two homes — flagged as a judgment call. | Fish Category, Plant Category left NR: paper never assigns a life-stage or category term to its own fish (only a stocking-weight range, ‘c. 90-110 g’) or its own spinach beyond ‘baby spinach (Spinacia oleracea)’. Water classification, pHOptimal, FUE AP, FUE HYD, WUE, EC, SPAD, Leaf count, Plant fresh weight, Lat/Long: none reported anywhere in the paper. Tissue nitrate AP/HYD = NR (paper measured spinach shoot minerals, N/P/K/Ca/Mg/S/Fe/Cu/Mn/Zn/B, and off-flavor GSM/MIB, but never nitrate specifically in plant tissue). Mineral leaf-tissue values (Fe,Cu,Mn,Zn,B,N,P,K,Ca,Mg,S) and spinach-tissue GSM/MIB recorded separately in plant_measurements.csv, not here. | Biological system already in use = N: ‘250 mL filter starter (Easystart) was added to each biofilter tank one week before (27 April) and six days after (10 May) the fish stocking (4 May)’ (Methods 2.1, p.3) describes a newly started, not pre-established, biofilter; the whole study is explicitly framed around measuring the onset of nitrification in a fresh system. | pH Buffers = N: no chemical buffer (e.g. sodium bicarbonate) was added to either system during the trial; Discussion (p.11) attributes the RAS pH drop after day 30 to ‘the lack of alkalinity management’ and attributes aquaponic pH stability to passive plant nutrient uptake (root H+/OH- exchange), not to an added buffer. | Nutrient supplemented = Y (aquaponics arm only, this row): modified Fe/Mn/Zn/Mo/K micronutrient solution added as needed plus daily spray; paired hydroponic control instead received Substral nutrient solution (manufacturer N 6%, P 1.3%, K 5%, S 0.6%, Cl <0.5%) biweekly plus daily spray — both are ‘Y’ in their own right but this row’s Details field describes the aquaponic dosing with the hydroponic comparison appended for context.
Plant Measurements
| Trial | System | Category | Analyte | Value | Unit | Sig. | Location |
|---|---|---|---|---|---|---|---|
| atiqueAquaponicsBeneficialTerms2022-T1 | AP | mineral | Fe | 523.3 ± 75.05 | mg/kg DM | p<0.05 | Table 3 (p.6) |
| atiqueAquaponicsBeneficialTerms2022-T1 | HYD | mineral | Fe | 143.3 ± 15.25 | mg/kg DM | p<0.05 | Table 3 (p.6) |
| atiqueAquaponicsBeneficialTerms2022-T1 | AP | mineral | Cu | 37.30 ± 12.70 | mg/kg DM | ns | Table 3 (p.6) |
| atiqueAquaponicsBeneficialTerms2022-T1 | HYD | mineral | Cu | 49.30 ± 9.60 | mg/kg DM | ns | Table 3 (p.6) |
| atiqueAquaponicsBeneficialTerms2022-T1 | AP | mineral | Mn | 403.3 ± 40.41 | mg/kg DM | ns | Table 3 (p.6) |
| atiqueAquaponicsBeneficialTerms2022-T1 | HYD | mineral | Mn | 366.6 ± 246.84 | mg/kg DM | ns | Table 3 (p.6) |
| atiqueAquaponicsBeneficialTerms2022-T1 | AP | mineral | Zn | 526.6 ± 142.9 | mg/kg DM | p<0.05 | Table 3 (p.6) |
| atiqueAquaponicsBeneficialTerms2022-T1 | HYD | mineral | Zn | 206.6 ± 55.07 | mg/kg DM | p<0.05 | Table 3 (p.6) |
| atiqueAquaponicsBeneficialTerms2022-T1 | AP | mineral | B | 120.0 ± 0.00 | mg/kg DM | p<0.0001 | Table 3 (p.6) |
| atiqueAquaponicsBeneficialTerms2022-T1 | HYD | mineral | B | 32.30 ± 8.08 | mg/kg DM | p<0.0001 | Table 3 (p.6) |
| atiqueAquaponicsBeneficialTerms2022-T1 | AP | mineral | N | 38.70 ± 3.00 | g/kg DM | p<0.005 | Table 3 (p.6) |
| atiqueAquaponicsBeneficialTerms2022-T1 | HYD | mineral | N | 57.50 ± 2.61 | g/kg DM | p<0.005 | Table 3 (p.6) |
| atiqueAquaponicsBeneficialTerms2022-T1 | AP | mineral | P | 6.06 ± 1.10 | g/kg DM | p<0.05 | Table 3 (p.6) |
| atiqueAquaponicsBeneficialTerms2022-T1 | HYD | mineral | P | 9.40 ± 1.55 | g/kg DM | p<0.05 | Table 3 (p.6) |
| atiqueAquaponicsBeneficialTerms2022-T1 | AP | mineral | K | 64.60 ± 5.68 | g/kg DM | p<0.05 | Table 3 (p.6) |
| atiqueAquaponicsBeneficialTerms2022-T1 | HYD | mineral | K | 83.30 ± 8.96 | g/kg DM | p<0.05 | Table 3 (p.6) |
| atiqueAquaponicsBeneficialTerms2022-T1 | AP | mineral | Ca | 36.60 ± 3.51 | g/kg DM | p<0.0001 | Table 3 (p.6) |
| atiqueAquaponicsBeneficialTerms2022-T1 | HYD | mineral | Ca | 7.26 ± 0.35 | g/kg DM | p<0.0001 | Table 3 (p.6) |
| atiqueAquaponicsBeneficialTerms2022-T1 | AP | mineral | Mg | 16.60 ± 1.52 | g/kg DM | p<0.005 | Table 3 (p.6) |
| atiqueAquaponicsBeneficialTerms2022-T1 | HYD | mineral | Mg | 5.80 ± 1.01 | g/kg DM | p<0.005 | Table 3 (p.6) |
| atiqueAquaponicsBeneficialTerms2022-T1 | AP | mineral | S | 3.56 ± 0.41 | g/kg DM | p<0.05 | Table 3 (p.6) |
| atiqueAquaponicsBeneficialTerms2022-T1 | HYD | mineral | S | 5.63 ± 0.47 | g/kg DM | p<0.05 | Table 3 (p.6) |
| atiqueAquaponicsBeneficialTerms2022-T1 | AP | biochemistry | MIB (shoot) | 704.4 ± 73.08 | ng/kg | p<0.05 vs start (A); p<0.05 vs HYD (a) | Table 7 (p.10), end of 42-day experiment (14 June) |
| atiqueAquaponicsBeneficialTerms2022-T1 | HYD | biochemistry | MIB (shoot) | 278.00 ± 158.2 | ng/kg | p<0.05 vs start (A); p<0.05 vs AP (a) | Table 7 (p.10), end of 42-day experiment (14 June) |
| atiqueAquaponicsBeneficialTerms2022-T1 | AP | biochemistry | MIB (root) | 1496.6 ± 998.2 | ng/kg | ns vs start; ns vs HYD | Table 7 (p.10), end of 42-day experiment (14 June) |
| atiqueAquaponicsBeneficialTerms2022-T1 | HYD | biochemistry | MIB (root) | 300.50 ± 80.48 | ng/kg | p<0.05 vs start (A); ns vs AP | Table 7 (p.10), end of 42-day experiment (14 June) |
| atiqueAquaponicsBeneficialTerms2022-T1 | AP | biochemistry | GSM (shoot) | 8.68 ± 2.50 | ng/kg | p<0.05 vs start (A); ns vs HYD | Table 7 (p.10), end of 42-day experiment (14 June) |
| atiqueAquaponicsBeneficialTerms2022-T1 | HYD | biochemistry | GSM (shoot) | 7.87 ± 2.24 | ng/kg | p<0.05 vs start (A); ns vs AP | Table 7 (p.10), end of 42-day experiment (14 June) |
| atiqueAquaponicsBeneficialTerms2022-T1 | AP | biochemistry | GSM (root) | 3579.8 ± 1682.8 | ng/kg | ns vs start; p<0.05 vs HYD (a) | Table 7 (p.10), end of 42-day experiment (14 June) |
| atiqueAquaponicsBeneficialTerms2022-T1 | HYD | biochemistry | GSM (root) | 191.80 ± 48.78 | ng/kg | ns vs start; p<0.05 vs AP (a) | Table 7 (p.10), end of 42-day experiment (14 June) |
| atiqueAquaponicsBeneficialTerms2022-T1 | baseline | biochemistry | MIB (shoot) | 1079.4 | ng/kg | not applicable (pre-treatment baseline) | Table 7 (p.10), start (5 May), before AP/HYD split |
| atiqueAquaponicsBeneficialTerms2022-T1 | baseline | biochemistry | MIB (root) | 1260.6 | ng/kg | not applicable (pre-treatment baseline) | Table 7 (p.10), start (5 May), before AP/HYD split |
| atiqueAquaponicsBeneficialTerms2022-T1 | baseline | biochemistry | GSM (shoot) | 134.4 | ng/kg | not applicable (pre-treatment baseline) | Table 7 (p.10), start (5 May), before AP/HYD split |
| atiqueAquaponicsBeneficialTerms2022-T1 | baseline | biochemistry | GSM (root) | 212.8 | ng/kg | not applicable (pre-treatment baseline) | Table 7 (p.10), start (5 May), before AP/HYD split |