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Which aquaponics setup grows better lettuce?
Aquaponics combines fish farming and plant growing in one system, but not every way of running it suits lettuce. In a greenhouse trial at the Universidad Autónoma Chapingo in Mexico, lettuce in a conventional recirculating aquaponics system yielded 10.93 kg per square metre, while lettuce in a biofloc-based system yielded only 0.37 kg.
Biofloc technology encourages microbial biomass in the fish water by adjusting its carbon to nitrogen (C:N) ratio, and it has been used to improve feed efficiency and water quality in tilapia farming. The Chapingo team wanted to know how lettuce would do in an aquaponics system built around biofloc, compared with a conventional aquaponics system with simple recirculation, both stocked with tilapia (Cerón-Argüelles et al., 2026).
What this means for your grow
If you grow lettuce in aquaponics, this trial favours the conventional recirculating setup: its plants were about 29 times heavier at harvest. The authors suggest the biofloc system did poorly partly because its microbial community had not had time to mature, so the result describes a newly started biofloc system run for one short lettuce crop, not biofloc in general. The two systems also differed in grow bed, feed rate and fish density, so the trial cannot say which of those differences mattered most.
What did the team do?
The team set up two aquaponics systems in a greenhouse, each replicated three times. The biofloc system used 170 L round polyethylene fish tanks run with 150 L of water, a settler to remove solids, a tub with nylon mesh for microbes to grow on, and a tub with a floating polystyrene raft for the lettuce. It was run at a C:N ratio of 12:1, with molasses as the carbon source. The conventional system grew its lettuce in a bed of tezontle laid in three layers of particle size: 8 mm at the bottom, 6 mm in the middle and 4 mm on top.
Lettuce ‘Sangria’ was sown in germination trays, transplanted 15 days after sowing and harvested 21 days after transplanting, at 21 plants per 0.6 square metres in both systems. The team weighed and measured the plants, analysed the nutrients in the leaves and in the water, and tracked water temperature, pH, EC (electrical conductivity), dissolved oxygen, ammonium, nitrite and nitrate.
What did they find?
- Far bigger plants in the conventional system. At harvest, lettuce in the conventional system averaged 312.31 g fresh weight per plant, against 10.73 g in the biofloc system. Dry weight was 61.17 g against 5.36 g. The authors put these at 29.1 and 11.41 times higher.
- More leaves, more leaf area. Plants in the conventional system had 28.0 leaves and 4 627.4 cm² of leaf area, against 9.33 leaves and 161.54 cm² in the biofloc system.
- Better-fed leaves. Leaves from the conventional system held more nitrogen, phosphorus, calcium and magnesium. Potassium was the exception: it was higher in the biofloc lettuce (4.74% against 2.25%).
- Very different water. At 21 days after transplanting, the biofloc water averaged pH 8.36 and EC 1.25 dS per metre, and the conventional system pH 6.26 and EC 2.15 dS per metre. Nitrate was 50.00 mg per litre in the biofloc water and 110.00 mg per litre in the conventional system.
- A coating on the roots. During the trial, a mucilaginous layer formed around the roots in the biofloc system. The authors suggest it may have acted as a barrier that restricted nutrient uptake.
What could it mean?
The authors conclude that the conventional recirculating system was more productive than the biofloc system, and that under the conditions and duration of their study, biofloc technology did not maximise lettuce yield. They suggest the biofloc system needs adjustments to its C:N ratio and time for its microbial communities to stabilise, and that other carbon sources could be tested. For now this is useful mainly to people designing or running aquaponics systems; it is not a tested recipe for a home setup.
What were the limitations?
- The authors say the biofloc system’s low performance may have been related to a nitrifying community that had not matured: the system started in April and ended in May, which they describe as too short to develop a stable microbial load.
- Although both systems held the same number of fish, the total fish biomass in the biofloc system was significantly lower, which the authors say reduced the nutrients available to the plants.
- Both systems used a ratio of plant growing area to fish water volume of 6:1, below the 10:1 the authors cite as optimal.
- Water temperature in both systems was below the optimal range of 28 to 32 °C reported for tilapia.
- The systems differed in more than one way: grow bed (tezontle bed or floating raft), biological filter (tezontle or plastic mesh), feed rate and fish density.
- The paper’s abstract and results do not always agree. The abstract gives the conventional system’s fresh weight as 321.31 g per plant and the biofloc system’s yield as 0.375 kg per square metre, while the results give 312.31 g (Table 1 and the text) and 0.37 kg (the text and conclusions). The abstract also lists potassium among the nutrients higher in the conventional system’s leaves, but Table 2 shows it higher in the biofloc lettuce. This post uses the results.
Trial details
- Who and where: Universidad Autónoma Chapingo, in a 195 m² greenhouse at the San Ignacio experimental field, Texcoco, State of Mexico, Mexico, at 2 240 m above sea level.
- When: the biofloc system ran from April to May (the year is not given). Lettuce was sown in germination trays, transplanted 15 days after sowing and harvested 21 days after transplanting.
- Crop: lettuce (Lactuca sativa) ‘Sangria’, 21 plants per 0.6 m² in both systems.
- Fish: tilapia, at 3 kg·m−3 in the biofloc system and 4 kg·m−3 in the conventional system. Feed: commercial formula 5015, at 5% of the feed ration in the biofloc system and 10% of biomass in the conventional system.
- Biofloc system: 170 L round polyethylene tanks (60 cm across) run with 150 L of water; a 70 L radial flow settler; a 40 L tub with 6 m of nylon mesh as a substrate for microbes; a 210 L tub (1 × 0.6 × 0.4 m) with a 1 inch polystyrene floating raft. C:N ratio 12:1, with molasses as the carbon source.
- Conventional system: simple recirculation, with a culture bed of tezontle in three layers: 8 mm (bottom), 6 mm (middle) and 4 mm (top).
- Water at 21 days after transplanting (biofloc / conventional): temperature 24.00 / 27.00 °C (not significantly different); pH 8.36 / 6.26; EC 1.25 / 2.15 dS·m−1; dissolved oxygen 4.40 / 4.56 mg·L−1; ammonium 0.10 / 1.60 mg·L−1; nitrite 0.30 / 2.16 mg·L−1; nitrate 50.00 / 110.00 mg·L−1. Over the trial, pH ranged from 8.0 to 8.7 in the biofloc system and 6.2 to 8 in the conventional system, and EC from 0.79 to 1.25 and 1.21 to 2.15 dS·m−1.
- Design: completely randomised design, two treatments, three replicates. Analysis of variance and Tukey’s test (α = 0.05) in SAS.
- Results (biofloc / conventional): fresh weight 10.73 / 312.31 g per plant; dry weight 5.36 / 61.17 g; leaves 9.33 / 28.0; leaf area 161.54 / 4 627.4 cm²; leaf area index 2.24 / 64.26; yield 0.37 / 10.93 kg·m−2. Leaf tissue nitrogen 0.45 / 1.03%, phosphorus 0.12 / 0.47%, potassium 4.74 / 2.25%, calcium 1.70 / 4.26%, magnesium 1.03 / 1.41%, iron 198.79 / 253.11 mg·kg−1, manganese 34.76 / 103.40 mg·kg−1. All differences significant (Tukey, p ≤ 0.05).
- Funding and conflicts of interest: the first author thanks CONACyT, now SECIHTI, for financial support for master’s studies. The authors declare no conflicts of interest.
- Publication: Revista Chapingo Serie Horticultura 32, e25014 (2026), https://doi.org/10.5154/r.rchsh.2025.10.014. Received 18 September 2025, accepted 16 April 2026.
- Not reported in the paper: the year of the trial, the light levels, air temperature, humidity and CO2 in the greenhouse, the number of fish, and the number of plants sampled.
Links
- The study: Comparison of lettuce yield in conventional aquaponics and biofloc systems
- The institution: Universidad Autónoma Chapingo
References
- Cerón-Argüelles, C. L., Salazar-Moreno, R., Pineda-Pineda, J., & Contreras-Cruz, L. F. (2026). Comparison of lettuce yield in conventional aquaponics and biofloc systems. Revista Chapingo Serie Horticultura, 32, e25014. https://doi.org/10.5154/r.rchsh.2025.10.014