Alternatives in Aquaculture Feeds
Brackish Aquaponics or Hydroponics
Jill Fisk is a Senior Research Associate in Aquaculture Production at Kentucky State University specializing in Environmental Science, Recirculating Aquaculture Systems (RAS) and Plant Science. Ms. Fisk’s current research centers on brackish hydroponic production methods and Pacific white shrimp production in RAS (Research Gate, n.d.).
In one of Ms. Fisk's studies, "Salinity impacts on aquaponic Kale Winterbor (Brassica oleracea): Production, water quality, and sensory properties" kales tolerance to brackish saltwater conditions was tested within an aquaponics system. This was done to determine water quality impact from kales growth in saline water and to establish consumer preferences for backish aquaponic raised kale. The study concluded that kale can be grown in salinity up to 20 ppt though it had a reduced growth rate at this level and grew progressively better at lower salinities. Consumers had increased willingness to pay when they understood the production method and they liked kale grown in 5 ppt salininty more than that grown in freshwater as the salinity reduced the "bitter" taste.
This study has implications for aquaponics and hydroponics as a whole but also for the possibility of alternative feed ingredients such as seaweed (Magbauna, 2024; Kamble, 2025; Nauta, 2025) to be grown in a brackish system alongside a saltwater fish species or shrimp, which would increase the harvest capacity for a brackish Recirculating Aquaculture System. This could also have implications for areas with limited access to fresh water and is an avenue of research that needs more study to determine plausibility. It should also be noted that Nile Tilapia are known to have good salinity tolerance up to 19ppt and maintain growth parameters in brackish water (Mjoun, 2010).
Red Seaweed (Rhodophyta) as a Feed Ingredient
Kamble (2025) is a literature review conducted to review the current data surrounding the inclusion of Red Seaweed species (Rhodophyta) in agricultural and aquacultural feeds. The review found that some red seaweed species can be fed as an aquacultural feed up to 30% of total feed without negative impacts, and stated that it has promising potential for replacing fishmeal in part as a protein source, though there are some uncovered amino acid requirements that would need supplementation and some Anti-Nutritional Factors such as phlorotannins and certain polysaccharides are present. However the study noted that combining multiple species of red seaweeds could help balance these negative impacts and deficiencies.
Some species such as Gracilaria corticata and Gracilaria verrucosa were noted as having been implemented with shrimp farming practices, improving water quality and reducing waste emissions. With other species demonstrating benefits as well.
In addition the review stated that inclusion of red seaweed species in feed can enhance immune response, provide anti-viral benefits, and promote aspects of gut health such as digestibility of feeds, enzymatic activity and microbial density. This information further supports the potential of brackish aquaponics and/or hydroponics demonstrating the positive effects of red seaweeds as an aquacultural feed additive or partial fishmeal replacement with or without brackish aquaponic growth.
Red Seaweed Salinity Tolerance
Nauta (2025) was a study performed to test various salinity level tolerance for Gracilariopsis longissima and Gracilaria gigas (red seaweed species). The study grew seaweed at multiple salinities between 5-30ppt and determined that 10-15ppt provided the highest growth rates but all salinities were tolerated. G. gigas was determined to be less sensitive to salinity changes but neither showed significant growth or performance issues at various salinities within the lower levels.
This has potential relation to Fisk (2025) and the demonstrated ability of kale to be grown within saline conditions as there is an overlap in salinity tolerance between kale and the red seaweed species in Nauta (2025). This could indicate that a single system could grow multiple crops such as kale and red seaweed in brackish water together. There is additional research necessary for this idea to have greater feasibility but there could be positive impacts for regions with low access to freshwater if they could grow multiple sources of food within an aquaponics or hydroponics system using available brackish water.
Seaweed Protein
Tadmor-Shalev (2026) performed a study to test salinity requirements and impacts of higher levels of salinity on seaweed growth with Gracilaria cornea, a red seaweed species. The study tested seaweed growth at levels of 30, 40, and 50 ppm salinity and discovered that not only could seaweed survive this hyper salinity stress, but it increased the protein content of the following seaweed harveseted. Harvesting date and salinity levels were also noted to have an impact on amino acid levels, harvesting on Day 14 of hypersalinic stress produced the highest amount of essential amino acids in the test group.
While this study may not have direct relation to the concept of brackish aquaponics or hydroponics, the ability to increase the protein level in a feed source through short term salinity increase could have implications for its use as a protein supplement or partial replacement in aquaculture feeds.
Citations
Fisk, J. C., Kershaw, J., Fleckenstein, L. J., & Ray, A. J. (2026). Salinity impacts on aquaponic Kale Winterbor (Brassica oleracea): Production, water quality, and sensory properties. Aquaculture Reports, 46, 103332. https://www.sciencedirect.com/science/article/pii/S2352513425007185#sec0005
Kamble, M. T., Wongprasert, K., Chavan, B. R., Daunde, V. V. Y., Palekar, G. K. R., Tayade, S. H., ... & Pirarat, N. (2025). Red seaweeds in aquaculture: Impacts on growth, immunity, antioxidant status, gene expression, and gut health. Annals of Animal Science. https://reference-global.com/download/article/10.2478/aoas-2025-0092.pdf
Research Gate. (n.d.). Jill Fisk. Research Gate. https://www.researchgate.net/profile/Jill-Fisk
Magbanua, T. O., & Ragaza, J. A. (2024). Selected dietary plant-based proteins for growth and health response of Nile tilapia Oreochromis niloticus. Aquaculture and Fisheries, 9(1), 3-19. https://www.sciencedirect.com/science/article/pii/S2468550X22000703
Nauta, R. W., Ariyati, R. W., Widowati, L. L., Debrot, A. O., & Rejeki, S. (2025). Effect of salinity on growth, agar content and gel strength for two agaroid seaweed species: Gracilariopsis longissima and Gracilaria gigas. Egyptian Journal of Aquatic Research. https://www.sciencedirect.com/science/article/pii/S1687428525000585
Mjoun, Kamal; Rosentrater, Kurt; and Brown, Michael L., (2010). TILAPIA: Environmental Biology and Nutritional Requirements. SDSU Extension Fact Sheets. 164.
https://openprairie.sdstate.edu/extension_fact/164
Tadmor-Shalev, N., Shemesh, E., Israel, Á., Ghermandi, A., Tchernov, D., & Brook, A. (2026). Salinity stress enhances protein content and amino acid profile in Gracilaria cornea (Rhodophyta). Scientific Reports. https://www.nature.com/articles/s41598-026-36828-0