A Scientific Investigation of Alternative Growing Methods to Cultivate Lactuca sativa

Metadata

• Cite key: fishbackScientificInvestigationAlternative2020
• Item type: Journal Article
• Authors: S. Fishback, S. Duncan
• Affiliation: Meadow Park Middle School, Beaverton, Oregon
• Journal: Journal of Emerging Investigators 3 (2020) 1-4
• Date: 04/2020
• Date added: [not reported]
• DOI: 10.59720/19-074
• Funding: [not reported]
• URL: https://doi.org/10.59720/19-074
• PDF: Fishback and Duncan - 2020 - A Scientific Investigation of Alternative Growing Methods to Cultivate Lactuca sativa.pdf

Opinion

A student-authored (middle-school-level) paper in the Journal of Emerging Investigators, comparing a single aquaponic raft system (goldfish) against a paired hydroponic raft system for lettuce. The design is genuine (11 seeds per system, daily height measurements, means/SD/growth-rate/R² reported over ~18 days) but very small-scale and unreplicated at the system level (n=1 tank per treatment, no true replication of the system, only of plants within it). The paper is transparent about its own weaknesses (goldfish nibbling roots, possible hydroponic under-fertilization) which is commendable, but most fish-side and plant-biomass metrics that would matter for an aquaponics literature review (stocking density, feed quantity, survival, absolute plant height/weight) are simply never reported. Useful mainly as a small, honest head-to-head growth-rate comparison, not as a source of quantitative aquaponic system performance data.

Abstract

Hydroponics is the process of planting seeds inside a solid growth medium instead of soil and providing them with nutrients that soil would normally provide. Aquaponics is a method of growing plants without soil, utilizing fish waste to fertilize plants. In this experiment, we compared both methods to observe if hydroponic nutrients and fish waste would produce plants with different heights when growing a widely cultivated vegetable like Lactuca sativa. Our hypothesis was that aquaponics would be a more efficient farming method in terms of growth per day and average height, since the method uses a natural fertilizer. The aquaponics system would simulate an open environment, helping the plants better adapt to the natural fertilizer provided by fish. At the beginning of the experiment, the plants in the aquaponics system were taller than those in the hydroponics system, but the hydroponics plants had a faster growth rate than aquaponics plants by the end of the experiment. However, the aquaponics system had a higher growth rate than the hydroponics system in the majority of the experimental timeframe, and had a higher average plant height. Therefore, the aquaponics system was a superior system to the hydroponics system, producing plants with better height by 0.4 centimeters on the final day, and higher average growth rate by 0.02329545455.

Summary

Two middle-school students built a paired raft (deep water culture) system to compare aquaponics (three goldfish providing waste as fertilizer) against hydroponics (a commercial nutrient solution dosed weekly) for growing lettuce (Lactuca sativa) from seed. Eleven seeds were sown directly into rockwool/LECA-filled net pots in each of two identical Styrofoam rafts floating in separate reservoirs, under shared LED lighting, and plant height was measured daily with a ruler for roughly two-and-a-half weeks. The aquaponic system produced a slightly higher average growth rate (0.253 cm/day vs. 0.230 cm/day) and ended with an average plant height 0.4 cm taller than the hydroponic system, leading the authors to conclude aquaponics was the superior method. No fish growth, feed quantity, survival, or water-chemistry data are reported; the only aquaponic-side outcome captured quantitatively is plant height/growth rate. The authors themselves flag design weaknesses, including exposed plant roots being nibbled by the goldfish and possible under-dosing of the hydroponic nutrient solution relative to a prior, smaller reservoir.

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Experiment data

• Location: Beaverton, Oregon, USA (Meadow Park Middle School, in collaboration with Terra Nova School of Science and Sustainability)
• Design: Two-arm comparison, one aquaponic raft/reservoir system (3 goldfish, no added nutrients) vs. one paired hydroponic raft/reservoir system (no fish, hydroponic nutrient solution dosed weekly); no replication at the system/tank level, 11 plants per system
• Replicates / n: 11 plants (seeds) per system; 3 of the 11 aquaponic seeds were defective and recorded as zero growth per the paper’s own convention (Methods, p.4; Figure 3 caption, p.2)
• Duration: ⚠️18 days per Figures 5-6 axis (Day 3-Day 18); Results text (p.2) separately describes the same dataset as gathered “over two weeks” (~14 days) — see Extraction notes
• Organisms: Lactuca sativa (lettuce) / Carassius auratus (goldfish)
• Statistics: Mean, standard deviation, daily growth rate, and R²-trendline fit reported (Figures 5-6); no inferential significance test (t-test, ANOVA, etc.) is reported anywhere comparing the aquaponic and hydroponic arms
• Plant height: Aquaponic system 0.4 cm taller than hydroponic on the final day (Abstract/Results, p.1-2); absolute mean values not stated in text (only in Figure 5, not read)
• Plant growth rate: Aquaponic 0.2528409091 cm/day vs. hydroponic 0.2295454545 cm/day by the end of the experiment (Results, p.2) — no dedicated schema column, recorded in Experimental Remarks

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Growth rate and plant height comparison

This paper: The aquaponic system had a higher average plant height (final-day margin +0.4 cm) and a higher average growth rate (0.2528409091 cm/day vs. 0.2295454545 cm/day) than the paired hydroponic system by the end of the trial (Results, p.2; Abstract, p.1). The aquaponic system’s advantage held for most of the trial (days 3-13 per Results, p.2, or “day 1 and day 13” per Discussion, p.3 — see Extraction notes) but the hydroponic system had a higher growth rate on the final measured day (day 14, coinciding with a hydroponic nutrient dose), which the authors attribute partly to goldfish nibbling exposed lettuce roots in the raft system, stunting aquaponic plant growth (Discussion, p.3).

Compared with:

• todo D’anna 2019 — deep water culture / “lettuce raft method” description, cited as the basis for the raft-system design (Introduction, p.1)
• todo Bernstein and Lenard 2018 — “Aquaponic Gardening Rules of Thumb,” cited generally for aquaponic design guidance (References #6)

System design and equipment

This paper: Both systems used an identical black plastic reservoir, a drilled Styrofoam raft, and net pots filled with rockwool and Lightweight Expanded Clay Aggregate (LECA) stones (Methods, p.4). The aquaponic reservoir held three Carassius auratus (goldfish) fed standard fish flakes daily, ad libitum, for two to three minutes; the hydroponic reservoir instead received one teaspoon of hydroponic nutrients every seven days (Methods, p.4). Both reservoirs shared two LED grow lights and received a 3.8 L weekly water top-up to offset evaporation (Methods, p.4). No pump, filter, or water-recirculation loop is described in either system — fish/nutrients and plant roots share the same static body of water directly.

Linked claims

• Aquaponics can produce comparable or better plant growth than hydroponics
• Exposed plant roots in raft systems are vulnerable to fish grazing

Citations to chase

• todo D’anna, C. (2019) — “Hydroponic Gardens: The Lettuce Raft Method,” The Spruce (design basis for the raft/DWC system used here)
• todo Bernstein, S. and Lenard, W. (2018) — “Aquaponic Gardening Rules of Thumb,” The Aquaponic Source

Extraction notes

Paper type: Confirmed experiment on full read (4 pages) — the authors built and ran their own paired aquaponic/hydroponic raft systems, collected daily height measurements over multiple weeks, and computed means, SD, growth rates, and R²-trendlines. It is not a review despite discussing background literature only in the Introduction (References 1-6 are all general background/design sources, not data comparisons).

Trial structure: One aquaponic arm = one trials.csv row (-T1). Per SCHEMA.md, only the aquaponic arm gets a row; the paired hydroponic arm’s data (nutrient dosing, final height/growth rate) is preserved in this note and in Experimental Remarks rather than as its own row.

Aquaponic component confirmed: Yes — this paper directly compares an aquaponic system (goldfish providing the only fertilizer input) against a hydroponic system (commercial nutrient solution, no fish) growing the same plant (lettuce) side by side. Both arms use the same raft/deep-water-culture design, differing only in fertilizer source.

Contradictions found (severity-tagged):

• ⚠️MATERIAL Trial duration. Results (p.2): “With the height data gathered over two weeks…” (~14 days). Figures 5 and 6 (p.3) both plot individually labelled data points from “Day 3” through “Day 18” (16 distinct days). These are not the same duration. The figures are the more specific, itemised source (individual labelled days) versus a rounded prose estimate, so 18 (days) is recorded in Fish trial duration (days) (used here as the shared fish+plant trial duration, since the two arms ran concurrently and no separate plant-duration column exists). The “two weeks” phrasing is noted as loose/approximate language. Affects: Fish trial duration (days) cell only.
• ⚠️MINOR Day-range wording. Discussion (p.3): “the aquaponics system has a sustained higher growth rate through day 1 and day 13.” Results (p.2): “higher average growth rate during days 3 through 13,” and the figures’ earliest labelled data point is Day 3, not Day 1. No cell is affected — there is no Day 1 data point to extract either way.
• Not flagged as a contradiction: three of the eleven aquaponic seeds were defective (Figure 3 caption, p.2: “Plants 2, 8, and 9 contained defective seeds”) while Figures 5/6 captions and the Results state “11 plants in each aquaponics and hydroponics system.” This is explained directly by the Methods (p.4): “Any of the plants that did not grow in the experiment were given a value of zero in all data and graphs.” Replicates (n) = 11 is recorded as stated, with this explanation noted rather than treated as a discrepancy.

Severity tally: 0 BLOCK, 1 MATERIAL, 1 MINOR → quality: ok (0 BLOCK and ≤2 MATERIAL per SCHEMA.md scoring table).

[not reported] / NR fields grouped by field:

• Fish: Fish Category, Initial Stock density, FCR, SGR, Protein/N/P/K, % of body weight, Fish size initial, Fish size final, Total Feed, Fish biomass created, Fish survival rate, Fish weight gain — the paper gives only a qualitative feeding description (“fed as much as they could eat for two to three minutes using standard fish flakes,” Methods p.4), no quantities, weights, or survival statement anywhere in the text.
• Water: Water type, Water classification, Daily Water exchange rate (only a weekly 3.8 L top-up volume is stated, not a % exchange rate; computing one would be derivation), Aq pH, pHOptimal, FUE AP, FUE HYD, WUE, Dissolved Oxygen, EC, Water temperature, TAN/NH4-N, NO2-N, NO3-N — no water chemistry of any kind is measured or reported in this paper.
• Plant: Plants/m², SPAD, Plant height (absolute value; only the +0.4 cm difference and per-system SD are given in text, see Growth rate section above), Leaf count, Plant fresh weight, Plant dry matter.
• Location: Lat/Long — only the school’s city/state (Beaverton, Oregon) is given, no coordinates.
• Other: Average room Temperature, Biological system already in use, Air supplement, Iron supplemented, Remineralization, pH Buffers, Funding, Date added.

Days Plant after transplant = NA: seeds were sown directly into rockwool inside net pots (“Eleven seeds were planted in each styrofoam raft…then a drop of water was squirted on each seed,” Methods p.4) — no transplanting step occurs in this design, so this field is not applicable rather than unreported.

Water recycle = NA: both systems are single static reservoirs holding the fish (or hydroponic nutrients) and the floating raft directly; no pump, filter, or recirculation loop between separate compartments is described anywhere.

AP / HYD columns: left NR. Per SCHEMA.md’s “Still open” section, the intended contents of these two columns are undefined in the current schema; the paper’s actual comparison values (final height difference, growth rates) are instead preserved in the note text and in Experimental Remarks as NO COLUMN items so the data is not lost.

Statistically analysed = N: the paper computes descriptive statistics only (mean, SD, growth rate, R²-trendline fit) and never uses the word “significant” or reports a p-value/test statistic anywhere comparing the two systems.

No NEEDS_OCR.md entry needed — the PDF has a clean, fully extractable text layer throughout (confirmed on full 4-page read).

New tags introduced: none — Meta/Type/Experiment, Meta/Region/North-America, Meta/Fish/Goldfish, and Meta/Plant/Lettuce all reused exactly as already spelled in existing vault notes (abbeyBasilOcimumBasilicum2022/ferratiAssessmentNAlkylamideContent2025 for Goldfish; andersonGrowthTissueElemental2017/tadesseComprehensiveComparisonLettuce2023 for Lettuce; abbeyBasilOcimumBasilicum2022/wilsonComparisonAquaponicsHydroponics2017 for North-America).

New wikilink targets introduced: S. Fishback, S. Duncan (no existing author notes in vault to match against), Lactuca sativa, Carassius auratus, Plant height, Aquaponics can produce comparable or better plant growth than hydroponics, Exposed plant roots in raft systems are vulnerable to fish grazing.

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Source: Fishback and Duncan - 2020 - A Scientific Investigation of Alternative Growing Methods to Cultivate Lactuca sativa.pdf

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Data Tables

Structured data extracted from this paper into the vault's trials.csv / plant_measurements.csv datasets. Fields the paper didn't report are omitted. Download the full datasets (measurements).

Trial Parameters

fishbackScientificInvestigationAlternative2020-T1

Fish

Field	Value
Fish	Carassius auratus (goldfish)
Feed routine	Daily
Feed regime	Ad libitum (“as much as they could eat”) for two to three minutes, standard fish flakes (Methods, p.4)
Fish trial duration (days)	⚠18

Water

Field	Value
Water volume in the system	75

Plant

Field	Value
Plant	Lactuca sativa (lettuce)
Plant Category	Vegetable (p.1, “a widely cultivated vegetable like Lactuca sativa”)

System & Setup

Field	Value
System type	Raft / Deep Water Culture (paper’s own terms: “raft system”/“deep water culture”, p.1)
Media Details	Rockwool and Lightweight Expanded Clay Aggregate (LECA) stones inside net pots on a Styrofoam raft (Methods, p.4)
Artificial Lighting	Y (Two LED lights positioned above and shared equally between the aquaponic and hydroponic reservoirs (Methods, p.4))
Nutrient supplemented	N (None; the aquaponic arm relies solely on fish waste as the fertilizer source (paired hydroponic arm instead received one teaspoon of hydroponic nutrients every seven days, Methods p.4))
Equipment	Black plastic reservoir; Styrofoam raft with drilled holes; net pots; rockwool; LECA stones; two shared LED grow lights; ruler (plant height measurement); three Carassius auratus (goldfish)
Control Parameters	Light exposure equalized between aquaponic and hydroponic systems via two shared LED lights (Methods, p.4); identical reservoir, raft, net-pot, and substrate design used for both systems (Methods, p.4); weekly 3.8 L water top-up applied to both reservoirs to offset evaporation (Methods, p.4)

Site

Field	Value
Region	North-America
Country	USA

Results & Statistics

Field	Value
Measured Unit	cm (plant height, measured via ruler, Methods p.4)
Statistic Details	Mean, standard deviation, and daily growth rate calculated for all plants in each system; R-squared trendlines fitted in Figures 5-6 (Results p.2-3). No inferential significance test (t-test/ANOVA) reported.
Statistically analysed	N
Replicates (n)	11

Experimental Remarks: TRIAL DEFINITION: T1 = the aquaponic arm (Styrofoam raft + net pots with rockwool/LECA, reservoir containing three Carassius auratus goldfish, no external nutrients added) of a two-arm comparison against a paired hydroponic control (identical raft/reservoir/media, no fish, one teaspoon of hydroponic nutrients added every 7 days). Per SCHEMA.md, only the aquaponic arm gets a trials.csv row; the paper’s hydroponic-arm data is preserved below and in the note rather than as a separate row. | NOT DERIVED, left NR: Initial Stock density (3 goldfish, 75 L reservoir capacity stated, but no fish weight given anywhere, so kg/m3 cannot be recorded without derivation); FCR, SGR, Protein/N/P/K, % of body weight, Fish size initial/final, Total Feed, Fish biomass created, Fish survival rate, Fish weight gain - paper gives only a qualitative feeding description with no quantities, weights, or survival statement. Daily Water exchange rate NR - only a weekly 3.8 L top-up volume is stated (Methods p.4); converting to a % daily rate would be derivation. Plant height (absolute), Leaf count, Plant fresh weight, Plant dry matter, SPAD, Plants/m2 - not reported. | Fish Category, Water type, Water classification NR - paper does not categorise beyond species name and does not state water source or salinity classification. | Days Plant after transplant = NA - seeds sown directly into rockwool inside net pots (Methods p.4); no transplanting step in this design. | Water recycle = NA - both systems are single static reservoirs holding fish/nutrients and the raft directly; no pump, filter, or recirculation loop is described. | Water volume in the system = 75 L, as stated in Methods (p.4: “a reservoir that could carry 75 liters of water would be required”) - phrased as a required capacity rather than a directly confirmed fill measurement, but no alternative figure appears elsewhere in the paper, so this is not a conflict, just a note on phrasing. | AP and HYD columns left NR - per SCHEMA.md’s ‘Still open’ section the intended contents of these columns are undefined; the paper’s actual comparison values are preserved here instead (see below). | NO COLUMN: aquaponic average growth rate = 0.2528409091 cm/day; paired hydroponic average growth rate = 0.2295454545 cm/day, both ‘by the end of the experiment’ (Results, p.2). NO COLUMN: SD of plant height - aquaponic 1.283035635, hydroponic 1.20896502 (Results, p.2), reported without an accompanying absolute mean height value in running text (only the +0.4 cm AP-HYD difference on the final day is stated), so this SD cannot be attached to a value in the Plant height cell. NO COLUMN: paper’s headline finding - aquaponic system produced ‘plants with better height by 0.4 centimeters on the final day, and higher average growth rate by 0.02329545455’ relative to hydroponics (Abstract, p.1). NO COLUMN: three of the eleven aquaponic seeds were defective (Figure 3 caption, p.2) and, per Methods (p.4), non-growing plants were ‘given a value of zero in all data and graphs’ - so Replicates (n)=11 already includes these zero-growth plants by the paper’s own stated convention, not a discrepancy. | WARN-MATERIAL Fish trial duration: Results (p.2) states the height data were ‘gathered over two weeks’ (~14 days), but Figures 5 and 6 (p.3) display individually labelled data points from Day 3 through Day 18 (16 distinct days), and the Discussion (p.3) separately references a ‘day 14’ data point. ‘Two weeks’ and the 18-day-spanning figure axis are not reconcilable as the same duration; the figure axis is the more specific, itemised source, so 18 is recorded here as the defensible value. Affects: Fish trial duration (days) cell only (used here as the shared fish+plant duration since both arms ran concurrently and no separate plant-duration column exists). | WARN-MINOR: Discussion (p.3) states the aquaponic system had a sustained higher growth rate ‘through day 1 and day 13,’ but Results (p.2) describes the same finding as occurring ‘during days 3 through 13,’ and the figures’ earliest labelled data point is Day 3, not Day 1. No cell affected (no Day 1 data point exists to extract). | Feed routine/regime, Artificial Lighting, and Nutrient supplemented reflect the aquaponic arm specifically: fed daily ad libitum for 2-3 minutes on standard flakes (Methods p.4); two LED lights shared equally between both reservoirs (Methods p.4); no external nutrient solution added to the aquaponic reservoir, contrasted explicitly with the hydroponic reservoir’s weekly teaspoon dose (Methods p.4). | Authors’ own stated limitations (Discussion, p.3): goldfish nibbled on exposed plant roots in the raft system, possibly stunting aquaponic plant growth and contributing to its lower growth rate on day 14; the hydroponic nutrient dose (one teaspoon) was carried over unchanged from a prior, smaller-reservoir experiment, which the authors suggest may have under-fertilized the hydroponic arm.