Growth performance, nutrients and microbial dynamic in aquaponics systems as affected by water temperature
Metadata
- Cite key: khalilGrowthPerformanceNutrients2018
- Item type: Journal Article
- Authors: S. Khalil
- Affiliation: Department of Biosystems and Technology, Swedish University of Agricultural Sciences, Alnarp, Sweden
- Journal: European Journal of Horticultural Science 83(6) (2018) 388–394
- Date: 12/2018
- Date added: 2019-07-03
- DOI: 10.17660/eJHS.2018/83.6.7
- Funding: Partnership Horticulture
- URL: https://doi.org/10.17660/eJHS.2018/83.6.7
- PDF:
Department of Biosystems and Technology, Swedish University of Agricultural Sciences, Alnarp, Sweden and Khalil - 2018 - Growth performance, nutrients and microbial dynami.pdf
Opinion
A clean, small-scale, well-controlled climate-chamber comparison (AP vs HYD x 2 water temperatures, 3 replicates, repeated as two full experiments) with sound statistics (ANOVA/LSD, Kruskal-Wallis for the ordinal disease score). The single-author write-up is thin on numeric detail, though: leaf length/width, leaf nitrate, and total-N-in-system are only ever shown as bar charts with no numbers in the running text or a table, and Table 1’s fish/plant “biomass” values are ambiguous between individual-organism means and tank/gutter totals. Worth citing for the water-temperature effect on biofiltration, microbial density and disease incidence — a genuinely under-studied angle — but pull the growth numbers only from Table 1, not the figures.
Abstract
Aquaponics is an integrated production of fish and hydroponic crops with recirculation of the nutrient solution in which fish wastes are used as plant fertilizers. Development towards bioeconomical based cultivation system using industrial symbioses makes application of aquaponics systems in areas with surpluses or excess heat of great interest. Within the frame of these surpluses a significant amount of energy leaves the processes as low-grade heat through flue gas stacks and cooling water. However, little knowledge is available about the effect of low water temperature on the growth and microbial parameters in an aquaponics system. Investigations in the current study were thus carried out to study the effect of water temperature of 11°C compared with 21°C on plant growth, nutrient and microbial dynamic in aquaponic systems. Two cultivation systems (treatments) were used, an aquaponic system consisted of a fish tank, a biofilter and a plant unit, and a hydroponic system (control) consisted of a water tank and a plant unit. Basil and trout were used as model organisms. The experiment was run for a period of eight weeks and repeated over time. The results indicated good fish growth and better plant growth in aquaponics systems compared with hydroponic systems at both water temperatures. The growth, as indicated by plant biomass, leaf length and width as well as nitrate content in the leaves, was better at water temperature of 21°C compared with 11°C. Low water temperature of 11°C indicated a negative effect on biofiltration, microbial dynamics and disease incidence in the system. Negative correlation between the total nitrogen removal rate and low water temperature was also indicated.
Summary
Khalil compared an aquaponic system (fish tank + rotating biological contactor biofilter + NFT plant gutter) against a hydroponic control (water tank + NFT gutter on Hoagland/Arnon nutrient solution), each run at two water temperatures, 11°C and 21°C, in a climate chamber for eight weeks, with three replicate tanks/gutters per treatment and the whole experiment repeated once more over time (only the first repetition’s results are reported, since no difference between repetitions was found). Trout (Salmo trutta) and sweet basil (‘Genovese’) were the model organisms. Plant fresh and dry biomass, fish total body weight, leaf length/width, leaf nitrate, water macro/micronutrients, resident bacterial/fungal/pseudomonad counts, and basil root disease incidence were all higher (growth) or better (lower nitrate, lower disease, higher microbial density) at 21°C than at 11°C, in both aquaponics and hydroponics, with aquaponics consistently outperforming hydroponics at a given temperature. The paper argues that 11°C surplus/waste heat is too cold to use directly in aquaponics without pre-heating, and that basil is a good candidate crop for aquaponic cultivation at 21°C. Numeric detail for several outcomes (leaf length/width, leaf nitrate, total system nitrogen) exists only as bar charts in Figures 1–4, with no values given in the text or tables.
Experiment data
- Location: Climate chamber, Swedish University of Agricultural Sciences (Phytotron), Alnarp, Sweden
- Design: 2 (system: aquaponic vs hydroponic control) x 2 (water temperature: 11°C vs 21°C) factorial, 3 replicate tanks/gutters per treatment combination; whole experiment repeated as two independent runs over time (only run 1 reported)
- Replicates / n: 3 experimental units (tanks/gutters) per treatment; growth-parameter statistics based on 13 of 15 basil seedlings per unit and 8 trout per tank
- Duration: 8 weeks (56 days)
- Organisms: Trout (Salmo trutta) / Sweet basil, Ocimum basilicum ‘Genovese’
- Statistics: ANOVA with LSD test (P<0.05) for growth/nutrient/microbial data; Kruskal-Wallis test for the ordinal disease index; Minitab release 15
- Plant fresh biomass: 208.6 ± 0.3 g/plant (AP, 11°C) vs 154.6 ± 0.4 g/plant (HYD, 11°C); 235.7 ± 0.4 g/plant (AP, 21°C) vs 205.2 ± 0.5 g/plant (HYD, 21°C)
- Fish total body weight: start 68.6 ± 0.5 g (11°C) / 70.2 ± 0.4 g (21°C); harvest 149.4 ± 0.5 g (11°C) / 197.5 ± 0.3 g (21°C) — basis unclear, see ⚠️CHECK below
Water temperature treatment
This paper: Two water temperatures tested, 11°C and 21°C, held with an in-tank cooler; air temperature in the climate chamber 25°C day / 19°C night, 16 h photoperiod (natural light + 200 W m⁻² HPS lamps, 200 µmol m⁻² s⁻¹ at canopy).
Compared with:
- todo Nimmermark and Nilsson 2013 — waste-heat use in greenhouse production, cited as the basis for interest in <20°C surplus heat.
- todo Zhu and Chen 1999 — nitrification rate in fixed-film biofilters decreases at lower temperature; cited to explain the 11°C biofilter effect here.
- todo Nilsson and Nimmermark 2013 — herbs and lettuce suggested as candidate crops for cold aquaponics.
Plant growth
This paper: Fresh and dry basil biomass, leaf length and leaf width all higher at 21°C than 11°C, in both aquaponic and hydroponic systems; aquaponic > hydroponic at both temperatures (Table 1, Figures 1–2). Leaf length/width have no numeric values outside the bar charts (Figures 1, 2) — not extracted per the “never read a value off a figure” rule.
Compared with:
- todo Liu et al. 2014 — organic fertiliser increased lettuce leaf length/width and reduced nitrate content vs inorganic fertiliser, cited as consistent with this paper’s basil results.
Leaf nitrate content
This paper: Higher leaf nitrate at 11°C than 21°C in both systems; at 21°C, nitrate lower in hydroponic than aquaponic basil (Figure 3). No numeric values given anywhere in text or table — Figure 3 only, axis labelled “mg L⁻¹” (an unusual unit for leaf tissue; extraction/normalisation method not stated). Recorded NR in Tissue nitrate AP/HYD; see Extraction notes.
Water nutrient dynamics
This paper: Total nitrogen in the returned water higher in aquaponics than hydroponics overall (Figure 4, no numeric values in text). Macro/micronutrient panels (Tables 2–3) show P, K, Mg, S, Ca, Mn, B, Cu, Fe, Zn, Mo (mM) in the water returned to the fish tank from the plant unit, at both sampling points (weeks 4 and 8) and both temperatures. At 11°C, most elements increased in concentration after the plant unit relative to the fish-tank-at-start value; at 21°C, most elements decreased after the plant unit — read by the paper as good nutrient uptake by plants at 21°C and poor uptake at 11°C. K, iron, boron, zinc, copper, manganese and molybdenum were low, and phosphorus and calcium high, in the fish water relative to the standard Hoagland/Arnon basil solution used in the hydroponic control, at both temperatures — read as a fish-feed-driven nutrient imbalance. See Extraction notes for why none of this reaches trials.csv columns.
Microbial dynamics and disease incidence
This paper: General bacterial flora, general fungal flora and fluorescent pseudomonads (log CFU mL⁻¹, water samples) all lower at 11°C than 21°C, in both hydroponic and aquaponic systems, at both samplings (Table 4). Density lowest in the aquaponic water before the biofilter; increased after biofiltration. Basil root disease index (0–4 necrosis scale) higher at 11°C than 21°C in both systems, and higher before the biofilter than after in the aquaponic system at 21°C (Table 5, Kruskal-Wallis). This is the paper’s stated novel contribution (“first to present information considering the microbial dynamics and disease incidence in aquaponics system using low water temperature”).
Linked claims
- Aquaponics outperforms hydroponics on plant growth under matched conditions
- Low water temperature reduces biofilter nitrification efficiency
- Water temperature affects resident microflora density in recirculating systems
- Fish feed can create a plant nutrient imbalance in aquaponics
Citations to chase
- todo Nimmermark, S. and Nilsson, U. (2013) — waste heat for greenhouse production
- todo Zhu, S. and Chen, S. (1999) — impact of temperature on nitrification rate in fixed film biofilters
- todo Liu, C.-W. et al. (2014) — nitrogen fertilizers, growth and nitrate content of lettuce
- todo Rakocy, J.E., Masser, M.P. and Losordo, T.M. (2006) — recirculating aquaculture tank production systems: aquaponics
- todo Graber, A. and Junge, R. (2009) — aquaponic systems, nutrient recycling from fish wastewater
Extraction notes
⚠️BLOCK — Aq pH. Results (p.392, immediately after Table 5): “At both temperatures, the pH value in the fish tank was within the range 7.1–7.5 and was adjusted daily after biofiltration, by the addition of acid, to a value around 6.0.” Discussion, Water quality parameters (p.393): “In the present study, the pH at both temperatures investigated was adjusted daily to a value of 5.6, according to the recommendation by Hoagland and Arnon (1950), before the nutrient solution was circulated to the plant unit.” Both sentences describe the same event — the daily acid-adjustment of the aquaponic loop water after the biofilter and before the plant unit — but give different target values (6.0 vs 5.6) with no reconciling statement. Neither is flagged as a typo or superseded; both read as the paper’s own stated fact. Not reconcilable from the text. Aq pH recorded UNCLEAR for both trials; raw (unadjusted) fish-tank pH range 7.1–7.5 recorded in remarks as context only, not as the Aq pH value. Added to REVIEW.md.
⚠️CHECK — Fish size initial/final (Table 1, p.390). Table 1 is titled “Mean plant and fish biomass (g)… n=13 for plants, n=8 for fish,” but the fish rows are labelled “Total biomass at start” / “Total biomass at harvest.” Two readings are defensible: (a) mean individual fish weight (8.6–8.8 g at start growing to ~18–25 g at harvest), by analogy with the plant rows in the same table, which are unambiguously per-plant means (13 individual basil plants; confirmed by the text: “data on 13 of the 15 plants used in the plant unite were available”); or (b) total combined biomass of the 8 fish in one tank (68.6–70.2 g start, 149.4–197.5 g harvest), taking the row label “Total biomass” literally. The paper never states which. This is exactly the “individual mean vs tank biomass” case named in SCHEMA.md. Recorded the literal table figures (68.6 ± 0.5 / 70.2 ± 0.4 g start; 149.4 ± 0.5 / 197.5 ± 0.3 g harvest) under Fish size initial/final, taking the per-fish-mean reading as clearest-basis (parallels the plant convention in the same table), with the tank-total alternative noted here and in Experimental Remarks. Added to REVIEW.md — this changes whether “Fish weight gain” for a single trout is ~10 g or ~80–125 g.
Not flagged as a contradiction: Table 2 and Table 3’s “Hydroponic system” baseline columns show identical numeric values (P=2, K=11, Mg=1, S=1.13, Ca=4.5, Mn=0.005, B=0.03, Cu=0.00075, Fe=0.04, Zn=0.004, Mo=0.0005) but different significance letters between the two tables. This is because each table is its own separate ANOVA (11°C data vs 21°C data); the letters are not meant to be compared across tables. No cell affected.
[not reported]: FCR, SGR, feed protein/N/P/K composition, Total Feed (kg), Fish biomass created (kg — not derived, see below), Fish survival rate, Fish weight gain, Initial Stock density (kg/m³), Water recycle (L/min), Water type, Water classification, Daily Water exchange rate, pHOptimal, FUE AP, FUE HYD, WUE, Dissolved Oxygen (monitored daily per Methods but no values given), TAN/NH4-N, NO2-N, NO3-N (Figure 4 shows “total nitrogen,” not nitrate-N specifically, and gives no numbers in text/table), Fish Category, Plant Category, Days Plant after transplant (see UNIT CONVERSION note), Plants/m², SPAD, Plant height, Leaf count, Tissue nitrate AP/HYD (Figure 3 only, no numeric values), Lat/Long.
NOT DERIVED, left NR: Fish biomass created (kg) and Fish weight gain (g/fish) — Table 1 gives start and harvest totals but the paper never states the gain itself, and computing it would additionally require resolving the ⚠️CHECK above about what the totals represent; not derived per the no-derivation rule. FCR and SGR — feed rate (1% body weight/day) and growth data are both present but FCR/SGR are never stated as such.
UNIT CONVERSION ONLY: 8-week experimental duration → 56 days (Fish trial duration, Days Plant after transplant).
NO COLUMN (routed to Experimental Remarks on both trial rows):
- Table 2 (11°C) / Table 3 (21°C): macro/micronutrient content (P, K, Mg, S, Ca, Mn, B, Cu, Fe, Zn, Mo, mM) of water returned to the fish tank from the plant unit, at two sampling points, vs the hydroponic-solution baseline and the fish-tank-at-start baseline. No dedicated trials.csv column exists for general water macro/micronutrients (Protein/N/P/K columns are feed-composition only).
- Table 4: general bacterial flora, general fungal flora, fluorescent pseudomonads (log CFU mL⁻¹) in hydroponic water and aquaponic water before/after biofilter, both temperatures, both samplings. Water-column microbiology, not plant-tissue — excluded from plant.csv per SCHEMA.md, and no trials.csv column exists either.
- Table 5: basil root disease index (0–4 necrosis scale), hydroponic vs aquaponic-before-biofilter vs aquaponic-after-biofilter, both temperatures, both samplings.
- Hydroponic control’s own nutrient solution: Hoagland and Arnon (1950) standard basil solution, pH 5.8, EC 2.2 dS m⁻¹, daily monitored and compensated (Methods, p.389). No HYD-specific pH/EC columns exist in the schema; the single
Aq pH/ECcolumns are understood to describe the aquaponic loop.
Water panel excluded from plant.csv (report item 7): Tables 2 and 3 are water chemistry (returned water to the fish tank), not plant tissue, so per SCHEMA.md they are excluded from plant_measurements.csv entirely and are noted above as NO COLUMN in trials.csv remarks instead. This is flagged here as the SCHEMA.md instruction requires saying so if a water panel seems too valuable to discard rather than silently dropping it.
Why plant.csv is 0 rows (report item 6): The only candidate plant-tissue analyte is leaf nitrate (Figure 3), which already has a dedicated home in trials.csv (Tissue nitrate AP/Tissue nitrate HYD) rather than plant.csv, consistent with how the vault’s other papers with a dedicated tissue-nitrate column have handled it (e.g. alcarrazQualityLettuceLactuca2018). It is NR there because it exists only as a bar chart with no numbers in text or table. No chlorophyll, other tissue minerals, proximate, or plant-tissue microbial-count data are reported anywhere in the paper — the only microbial counts (Table 4) are water-column, not plant-tissue.
Judgment call — fish naming: Methods calls the model fish “trout (Salmo trutta)”; the Conclusion calls it “brown trout.” Salmo trutta is indeed the scientific name for brown trout, so this is consistent terminology, not a contradiction. Recorded as “Trout (Salmo trutta)” in the Fish column.
Nutrient supplementation judgment call: Methods describes the hydroponic control receiving a standard Hoagland/Arnon nutrient solution, and describes the aquaponic system purely in terms of fish tank + biofilter + plant unit with no nutrient solution mentioned. Given the paper’s explicit framing of aquaponics as relying solely on fish waste (Introduction) and the parallel-structure methods description that mentions a nutrient solution only for the hydroponic arm, Nutrient supplemented is recorded N for the aquaponic trial rows (no external nutrient solution added), with the hydroponic solution detail noted in Nutrient supplementedDetails for context. This is an inference from methodological contrast rather than an explicit negation sentence — flagged here in case the user judges this too permissive a reading of “stated absent.”
Source: Department of Biosystems and Technology, Swedish University of Agricultural Sciences, Alnarp, Sweden and Khalil - 2018 - Growth performance, nutrients and microbial dynami.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
khalilGrowthPerformanceNutrients2018-T1
Fish
| Field | Value |
|---|---|
| Fish | Trout (Salmo trutta) |
| % of body weight | 1 |
| Fish size initial | 68.6 +/- 0.5 |
| Fish size final | 149.4 +/- 0.5 |
| Feed routine | Once daily, hand-fed |
| Feed regime | Commercial pellet feed at 1% of fish body weight per day |
| Fish trial duration (days) | 56 |
Water
| Field | Value |
|---|---|
| Water volume in the system | 50 (fish tank only, per replicate) |
| Water temperature | 11 |
Plant
| Field | Value |
|---|---|
| Plant | Sweet basil (Ocimum basilicum ‘Genovese’) |
| Details | 15 seedlings per gutter, rockwool cubes 2x2x4 cm (Grodan, NL); NFT irrigation |
| Days Plant after transplant | 56 |
| Plant fresh weight | 208.6 +/- 0.3 |
| Plant dry matter | 164.2 +/- 0.3 |
System & Setup
| Field | Value |
|---|---|
| System type | NFT (Nutrient Film Technique) |
| Media Details | Rockwool cubes (Grodan, NL), 2 x 2 x 4 cm; rotating biological contactor biofilter between fish tank and plant gutter |
| pH Buffers | Y (Daily acid addition to lower aquaponic-loop pH after biofiltration and before the plant unit; target value conflicts between two passages in the paper, see WARN-BLOCK Aq pH in the note) |
| Climate control | Y (Climate chamber, air temp 25 degC day / 19 degC night; water temperature held at 11 degC by an in-tank cooler) |
| Artificial Lighting | Y (16 h photoperiod, natural light supplemented with high-pressure sodium lamps (200 W m-2); 200 umol m-2 s-1 at canopy level) |
| Nutrient supplemented | N (No external nutrient solution described for the aquaponic system (fish-waste-fed only, per system design contrast in Methods); hydroponic control received standard Hoagland and Arnon (1950) basil solution, pH 5.8, EC 2.2 dS/m, daily monitored/compensated) |
| Equipment | In-tank water cooler; rotating biological contactor biofilter; NFT gutters; recirculation pump (model NR); high-pressure sodium lamps |
| Control Parameters | Water temperature (11 degC, setpoint); air temperature (25 degC day / 19 degC night); photoperiod (16h); aquaponic-loop pH (adjusted daily by acid addition, target value conflicts, see remarks) |
| Combination | Trout (Salmo trutta) and sweet basil (‘Genovese’); aquaponic vs hydroponic control, NFT system, tested at two water temperatures (11 degC vs 21 degC) |
Site
| Field | Value |
|---|---|
| Region | Europe |
| Country | Sweden |
| Average room Temperature | 19-25 (range only; 19 degC night / 25 degC day setpoints, climate chamber) |
Results & Statistics
| Field | Value |
|---|---|
| Measured Unit | g plant-1 (fresh weight, Table 1); g plant-1 (dry weight, Table 1) |
| Statistic Details | ANOVA with LSD test, P<0.05 (Minitab release 15); Kruskal-Wallis test for disease incidence (non-parametric) |
| Statistically analysed | Y |
| Replicates (n) | 3 |
| AP | 208.6 |
| HYD | 154.6 |
Experimental Remarks: TRIAL DEFINITION: T1 = aquaponic system at water temperature 11 degC (fish tank + rotating biological contactor biofilter + NFT plant gutter), 3 replicate units. Paired control = hydroponic system at 11 degC (water tank + NFT gutter, Hoagland/Arnon basil solution), recorded in HYD columns. | WARN-BLOCK Aq pH: Results p.392 states ‘the pH value in the fish tank was within the range 7.1-7.5 and was adjusted daily after biofiltration, by the addition of acid, to a value around 6.0’; Discussion p.393 states ‘the pH at both temperatures investigated was adjusted daily to a value of 5.6, according to the recommendation by Hoagland and Arnon (1950), before the nutrient solution was circulated to the plant unit.’ Both describe the same daily post-biofilter, pre-plant-unit acid adjustment step with different target values (6.0 vs 5.6); no reconciling statement. Recorded UNCLEAR. Raw (pre-adjustment) fish-tank pH range 7.1-7.5 noted for context only, not as the Aq pH value. UNRESOLVED, see REVIEW.md. | WARN-CHECK Fish size initial/final: Table 1 (p.390) is titled ‘Mean plant and fish biomass (g)…n=8 for fish’ but the fish rows are labelled ‘Total biomass at start’ / ‘Total biomass at harvest.’ Two readings are defensible: (a) mean individual fish weight (68.6 +/- 0.5 g start, 149.4 +/- 0.5 g harvest), by analogy with the same table’s unambiguously per-plant rows (confirmed individual, n=13 of 15 basil plants per text); or (b) total combined biomass of the 8 fish in one tank. Per-fish-mean reading recorded here, tank-total alternative noted. UNRESOLVED, see REVIEW.md. | UNIT CONVERSION ONLY: 8-week experimental duration -> 56 days (Fish trial duration, Days Plant after transplant). | NOT DERIVED, left NR: Fish biomass created and Fish weight gain (Table 1 gives start/harvest totals only, the gain itself is never stated, and computing it further depends on resolving the CHECK above); FCR and SGR (feed rate 1%/day and growth data given, but the ratio itself never stated); Initial Stock density (8 fish per 50 L tank given, never stated as kg/m3). | NO COLUMN: Table 2 (p.390) macro/micronutrient content (mM) of water returned to the fish tank from the plant unit at 11 degC. Sampling 1 (week 4), fish-tank-at-start / after-plant-unit: P 4.3/5.6; K 10.4/10.6; Mg 0.9/1.8; S 1.1/2.4; Ca 9.1/10.9; Mn 0.005/0.006; B 0.03/0.03; Cu 0.0008/0.0008; Fe 0.05/0.06; Zn 0.004/0.005; Mo 0.0004/0.0005. Sampling 2 (week 8): P 6.1/5.9; K 10.9/10.3; Mg 1.9/2.1; S 3.2/3.7; Ca 9.3/10.4; Mn 0.006/0.005; B 0.04/0.005; Cu 0.001/0.001; Fe 0.07/0.008; Zn 0.006/0.005; Mo 0.0006/0.0005. Hydroponic-solution baseline: P2, K11, Mg1, S1.13, Ca4.5, Mn0.005, B0.03, Cu0.00075, Fe0.04, Zn0.004, Mo0.0005 (all mM). No dedicated water macro/micronutrient columns exist in this schema. | NO COLUMN: Table 4 (p.392) water microbial counts (log CFU/mL) at 11 degC. Hydroponic system: bacterial 3.5/4.3 (samplings 1/2); fungal 2.2/2.1; pseudomonads 2.8/2.9. Aquaponic before biofilter: bacterial 2.5/3.2; fungal 1.9/1.6; pseudomonads 2.2/3.1. Aquaponic after biofilter: bacterial 3.1/4.3; fungal 2.8/2.3; pseudomonads 2.6/3.1. Water-column microbiology, not plant tissue - excluded from plant.csv per SCHEMA.md, and no trials.csv column exists either. | NO COLUMN: Table 5 (p.392) basil root disease index (0-4 necrosis scale) at 11 degC. Hydroponic 2/3 (samplings 1/2); aquaponic before biofilter 3/4; aquaponic after biofilter 3/4. | Fish Category, Plant Category, Water type, Water classification: NR, paper does not categorise these. | Lat/Long: NR - not stated anywhere in the paper; not derived from the Alnarp, Sweden institutional affiliation per the prime directive.
khalilGrowthPerformanceNutrients2018-T2
Fish
| Field | Value |
|---|---|
| Fish | Trout (Salmo trutta) |
| % of body weight | 1 |
| Fish size initial | 70.2 +/- 0.4 |
| Fish size final | 197.5 +/- 0.3 |
| Feed routine | Once daily, hand-fed |
| Feed regime | Commercial pellet feed at 1% of fish body weight per day |
| Fish trial duration (days) | 56 |
Water
| Field | Value |
|---|---|
| Water volume in the system | 50 (fish tank only, per replicate) |
| Water temperature | 21 |
Plant
| Field | Value |
|---|---|
| Plant | Sweet basil (Ocimum basilicum ‘Genovese’) |
| Details | 15 seedlings per gutter, rockwool cubes 2x2x4 cm (Grodan, NL); NFT irrigation |
| Days Plant after transplant | 56 |
| Plant fresh weight | 235.7 +/- 0.4 |
| Plant dry matter | 192.4 +/- 0.3 |
System & Setup
| Field | Value |
|---|---|
| System type | NFT (Nutrient Film Technique) |
| Media Details | Rockwool cubes (Grodan, NL), 2 x 2 x 4 cm; rotating biological contactor biofilter between fish tank and plant gutter |
| pH Buffers | Y (Daily acid addition to lower aquaponic-loop pH after biofiltration and before the plant unit; target value conflicts between two passages in the paper, see WARN-BLOCK Aq pH in the note) |
| Climate control | Y (Climate chamber, air temp 25 degC day / 19 degC night; water temperature held at 21 degC by an in-tank cooler) |
| Artificial Lighting | Y (16 h photoperiod, natural light supplemented with high-pressure sodium lamps (200 W m-2); 200 umol m-2 s-1 at canopy level) |
| Nutrient supplemented | N (No external nutrient solution described for the aquaponic system (fish-waste-fed only, per system design contrast in Methods); hydroponic control received standard Hoagland and Arnon (1950) basil solution, pH 5.8, EC 2.2 dS/m, daily monitored/compensated) |
| Equipment | In-tank water cooler; rotating biological contactor biofilter; NFT gutters; recirculation pump (model NR); high-pressure sodium lamps |
| Control Parameters | Water temperature (21 degC, setpoint); air temperature (25 degC day / 19 degC night); photoperiod (16h); aquaponic-loop pH (adjusted daily by acid addition, target value conflicts, see remarks) |
| Combination | Trout (Salmo trutta) and sweet basil (‘Genovese’); aquaponic vs hydroponic control, NFT system, tested at two water temperatures (11 degC vs 21 degC) |
Site
| Field | Value |
|---|---|
| Region | Europe |
| Country | Sweden |
| Average room Temperature | 19-25 (range only; 19 degC night / 25 degC day setpoints, climate chamber) |
Results & Statistics
| Field | Value |
|---|---|
| Measured Unit | g plant-1 (fresh weight, Table 1); g plant-1 (dry weight, Table 1) |
| Statistic Details | ANOVA with LSD test, P<0.05 (Minitab release 15); Kruskal-Wallis test for disease incidence (non-parametric) |
| Statistically analysed | Y |
| Replicates (n) | 3 |
| AP | 235.7 |
| HYD | 205.2 |
Experimental Remarks: TRIAL DEFINITION: T2 = aquaponic system at water temperature 21 degC (fish tank + rotating biological contactor biofilter + NFT plant gutter), 3 replicate units. Paired control = hydroponic system at 21 degC (water tank + NFT gutter, Hoagland/Arnon basil solution), recorded in HYD columns. | WARN-BLOCK Aq pH: same conflict as T1 - Results p.392 ‘adjusted daily after biofiltration…to a value around 6.0’ vs Discussion p.393 ‘adjusted daily to a value of 5.6’; both statements cover ‘both temperatures investigated,’ not just one, so the conflict applies identically here. Recorded UNCLEAR. UNRESOLVED, see REVIEW.md. | WARN-CHECK Fish size initial/final: same ambiguity as T1 (Table 1, p.390, ‘Total biomass at start/harvest’ vs n=8 caption) - per-fish-mean reading recorded (70.2 +/- 0.4 g start / 197.5 +/- 0.3 g harvest); tank-total-of-8-fish alternative possible. UNRESOLVED, see REVIEW.md. | UNIT CONVERSION ONLY: 8-week experimental duration -> 56 days. | NOT DERIVED, left NR: Fish biomass created, Fish weight gain, FCR, SGR, Initial Stock density - same reasons as T1. | NO COLUMN: Table 3 (p.391) macro/micronutrient content (mM) of water returned to the fish tank from the plant unit at 21 degC. Sampling 1 (week 4), fish-tank-at-start / after-plant-unit: P 4.3/3.9; K 11.2/7.3; Mg 1.2/0.8; S 1.2/0.9; Ca 10.3/9.5; Mn 0.005/0.004; B 0.04/0.03; Cu 0.0007/0.0006; Fe 0.05/0.04; Zn 0.005/0.003; Mo 0.0004/0.0003. Sampling 2 (week 8): P 4.1/3.2; K 10.8/6.5; Mg 0.9/0.5; S 1.2/0.7; Ca 9.8/8.4; Mn 0.005/0.003; B 0.04/0.002; Cu 0.0008/0.005; Fe 0.05/0.03; Zn 0.005/0.002; Mo 0.0005/0.0003. Hydroponic-solution baseline: P2, K11, Mg1, S1.13, Ca4.5, Mn0.005, B0.03, Cu0.00075, Fe0.04, Zn0.004, Mo0.0005 (all mM). No dedicated column. | NO COLUMN: Table 4 (p.392) water microbial counts (log CFU/mL) at 21 degC. Hydroponic system: bacterial 4.6/5.8 (samplings 1/2); fungal 3.5/3.7; pseudomonads 3.6/4.5. Aquaponic before biofilter: bacterial 2.8/3.9; fungal 2.6/2.5; pseudomonads 2.8/4.2. Aquaponic after biofilter: bacterial 5.5/5.7; fungal 3.4/3.3; pseudomonads 3.9/5.1. Water-column microbiology, excluded from plant.csv, no trials.csv column. | NO COLUMN: Table 5 (p.392) basil root disease index (0-4 scale) at 21 degC. Hydroponic 0/0 (samplings 1/2); aquaponic before biofilter 1/2; aquaponic after biofilter 1/0. | Fish Category, Plant Category, Water type, Water classification: NR. | Lat/Long: NR - not stated anywhere in the paper.