The appeal of nanomaterials lies in physics rather than chemistry alone. When matter is reduced to dimensions below roughly 100 nanometers, quantum effects and an enormous surface-area-to-volume ratio transform its behavior, dramatically enhancing electrical, magnetic, optical, and catalytic properties compared with the same material in bulk form. In water treatment, this translates into far greater capacity to capture and degrade contaminants. Aquaculture effluent is a complicated cocktail: total suspended solids, fecal matter and uneaten feed, phosphorus and nitrogen, ammonia, therapeutic drugs, and antifouling chemicals. The review identifies four principal classes of nanomaterials for tackling this burden: metal-containing nanoparticles, carbonaceous nanomaterials such as carbon nanotubes, zeolites, and dendrimers, each exploiting distinct mechanisms of adsorption, reduction, or catalytic oxidation.

Silver nanoparticles have emerged as the most intensively studied disinfection agents. Their antimicrobial power stems from a multi-pronged attack: the particles adhere to bacterial cell walls, penetrate them, and alter permeability, while silver ions interact with sulfur- and phosphorus-containing cellular components, inactivate enzymes by binding thiol groups, disrupt DNA replication, and trigger the release of reactive oxygen species. Laboratory studies cited in the review found that nanosilver at just 1 milligram per liter can suppress roughly 80 percent of a microbial population. Crucially, the authors caution against dosing water directly, since silver can bioaccumulate in cultured fish destined for human consumption. A safer strategy, they suggest, is coating filtration equipment with silver nanoparticles, allowing disinfection without exposing the animals themselves to the metal.

Nano zero-valent iron particles represent a second workhorse of nanoscale water remediation. These tiny iron particles act as powerful reducing agents, transferring electrons from their surfaces to pollutants and converting them into less harmful forms. Their redox activity, combined with adsorption and precipitation, has been harnessed to remove halogenated organic compounds, dyes, phenols, heavy metals, phosphates, and nitrates. One striking example is the treatment of hexavalent chromium, a highly carcinogenic contaminant: the iron nanoparticles reduce it to chromium(III), which precipitates as a far more stable hydroxide. Researchers have also documented effective lead removal using stabilized zero-valent iron, though concerns about the persistence of these particles in treated systems have driven efforts to immobilize them within porous support materials.

Zinc and iron oxide nanoparticles round out the water-treatment toolkit. Zinc oxide nanoparticles combine strong photocatalytic and oxidative capabilities with low cost and environmental compatibility, and their performance can be boosted by doping with metal ions, semiconductors, or reduced graphene oxide. Comparative studies found that zero-valent zinc outperformed iron, aluminum, and nickel nanoparticles in degrading octachlorodibenzo-p-dioxin, one of the most notorious persistent organic pollutants. Magnetic iron oxides, including magnetite, maghemite, and hematite, serve as efficient sorbents for heavy metals; magnetite nanosorbents have shown a maximum adsorption capacity of 36 milligrams of lead per gram of material, and their superparamagnetism allows easy recovery from treated water. Titanium dioxide, meanwhile, acts as a broad-spectrum photocatalyst, generating reactive oxygen species under even low ultraviolet light to destroy gram-positive and gram-negative bacteria, fungi, and viruses. In China, a sintered ceramic nanomaterial called Nano-863, prized for its light absorption and heat resistance, is already being used commercially to improve water quality for shrimp farming and to curb algal blooms.

Beyond water quality, the review highlights a less obvious frontier: fish reproduction. Captive fish often suffer reproductive dysfunction, and conventional hormonal therapies to induce spawning are undermined by the short half-life of gonadotropin-releasing hormone, which is rapidly degraded by enzymes in the pituitary, kidney, and liver. Repeated injections work but stress the animals. Nanoparticle carriers offer an elegant workaround. In common carp, researchers conjugated the hormone LHRH to chitosan nanoparticles and chitosan-gold nanoparticles, achieving sustained hormone release and fertilization rates of 87 percent and 83 percent respectively, compared with 74 percent in controls. In walking catfish, chitosan nanoparticles loaded with pheromones kept serum hormone levels elevated far longer than injections. Oral delivery of GnRHa via chitosan nanoparticles in goldfish, fed every three days over 40 days, prolonged hormone elevation and significantly increased egg diameter, while PLGA nanoparticles loaded with aromatase inhibitors have been used to produce monosex populations of tilapia and guppies.

Feeding efficiency is another target. Aquafeed is perishable, and its water-soluble components leach into ponds, driving pollution and nutrient loss while inflating costs. Nanotechnology addresses this by encapsulating active ingredients, protecting them until they reach the fish’s intestine. Nanoparticle-enriched feeds have demonstrably improved growth, survival, feed conversion ratio, specific growth rate, weight gain, blood parameters, and immune responses. Selenium nanoparticles enhanced growth and larval development in Nile tilapia, Asian sea bass, and gilthead sea bream at species-specific doses; iron nanoparticles upregulated growth-related genes in goldfish and improved muscle protein in catfish; and chitosan nanoparticles boosted immunity and survival in tilapia, common carp, and giant tiger prawns.

Disease management may be where nanotechnology delivers its most consequential impact. Antibiotic resistance is now documented throughout aquaculture, with tetracycline-, streptomycin-, and erythromycin-resistant Aeromonas hydrophila isolated from tilapia farms, alongside resistant strains of Staphylococcus aureus, Vibrio, Yersinia ruckeri, and Edwardsiella. Nanoparticles offer an alternative: engineered antibacterial surfaces, nanosensors that detect pathogens in water, and nano-encapsulated medicines delivered through feed. Diagnostic applications are already proving their worth. Magnetic nanoparticles coated with antibodies change color from red to blue when they bind viral antigens, enabling rapid detection of nervous necrosis virus in groupers, while unmodified gold nanoparticles have been used in similar colorimetric assays for spring viremia of carp and koi herpesvirus. Electrical nanosensors can now detect a single virus particle, and wireless tracking nanosensors permit individual fish health monitoring through data analysis.

Nanovaccines tackle the central dilemma of fish immunization: oral vaccines are destroyed by gastric digestion, while injections stress the animals. Polymer and lipid nanoparticles shield antigens from degradation in the gastrointestinal tract and deliver them intact to provoke mucosal, humoral, and cellular immunity. Challenge trials with nanovaccines against Listonella anguillarum succeeded in Asian carp and rainbow trout, chitosan-based oral nanovaccines protected tilapia against columnaris disease, and chitosan-coated membrane vesicles strengthened immunity against Piscirickettsia salmonis in zebrafish. Biosensors extend this precision medicine approach to physiology itself: enzyme-based immunosensors measure cortisol in fish blood to quantify stress, ranking stressors from air exposure to nitrite, while wireless implantable sensors transmit real-time blood glucose readings from swimming fish to receivers on shore.

The review is candid about the risks. Because of their minute size, nanoparticles readily cross cell membranes, and their chemical reactivity generates reactive oxygen species and free radicals that can cause inflammation, protein damage, and DNA deterioration. Silver nanoparticles smaller than 10 nanometers inflicted significantly more kidney and gill damage in rainbow trout than particles exceeding 35 nanometers, copper nanoparticles harmed liver, brain, and gill function in Mozambique tilapia, and zero-valent iron proved more toxic to embryonic medaka than to adults, underscoring the heightened vulnerability of early life stages. Nano waste, the authors warn, constitutes a novel form of pollution requiring careful tracking through food chains. Regulatory frameworks, including World Health Organization guidelines on manufactured nanomaterials, remain a work in progress, and the authors call for sustained investment, public-private partnerships, and technology transfer to developing nations. With emerging tools such as multi-omics toxicology and personalized fish health assessment on the horizon, they conclude that responsible integration of nanotechnology could help aquaculture meet global protein demands without compromising the ecosystems on which it depends.

Subject of Research: Applications of nanotechnology in sustainable aquaculture and fish health management

Article Title: Interventions of nanotechnology-based applications as a novel tool for sustainable aquaculture and fish medicines

Article References: Riyaz, R., Iqbal, G., Gargotra, P., & Ganie, P. A. (2025). Interventions of nanotechnology-based applications as a novel tool for sustainable aquaculture and fish medicines. Blue Biotechnology, 2(1), Article 12. https://doi.org/10.1186/s44315-025-00034-w

Image Credits: AI Generated

DOI: 10.1186/s44315-025-00034-w

Keywords: nanotechnology, aquaculture, nanoparticles, water treatment, fish health, nanovaccines, nanosensors, antibiotic resistance, fish nutrition, nanotoxicology, sustainability, chitosan

The context for the research is a global aquaculture system under strain. Fish provide the primary source of animal protein for many of the world’s poorest people, and demand has surged from roughly forty million tons in 2000 to more than ninety million tons by 2011, driven by population growth. That pressure has contributed to declining aquatic biodiversity in natural waters, pushing production toward farming. Fish farming itself is growing at about seven percent annually worldwide, and in Guinea’s forest region, rice-fish farming systems centered on species such as the African catfish Clarias gariepinus, Heterobranchus isopterus, and Nile tilapia have expanded considerably over the past decade. Yet the sector’s contribution remains limited by a critical bottleneck: the larval and fry rearing phase, where carnivorous young catfish require live prey or costly exogenous feed that rural producers often cannot access year-round.

The research team set out to answer a deceptively simple question: which organic fertilizer produces the most nutritious bloodworms? In September 2023, at an experimental site at the University of N’Zerekore, the researchers installed twenty-four rectangular ponds, each roughly one cubic meter, exposed to open air. Each pond received twenty-five cubic decimeters of a sand and gravel substrate, forty liters of borehole water, and an immediate application of fertilizer at a dose of 140 grams per cubic decimeter of substrate. Four fertilizers were tested: cow dung, rabbit droppings, poultry droppings, and pig manure. Three days after fertilization, the ponds were seeded with phytoplankton-rich pond water filtered through a 100-micrometer sieve to exclude unwanted macroinvertebrates, and three days later the ponds received an initial stocking of Chironomus sp larvae at a density of ten individuals per cubic decimeter of substrate. Mosquito netting covered the ponds to keep predators out.

The results on production density were striking. Rabbit droppings yielded the highest density of Chironomidae at approximately 2,797 individuals per cubic decimeter, followed by cow dung at 2,657, pig dung at 2,473, and poultry droppings at 2,432 individuals per cubic decimeter. Estimated biomass followed a slightly different ranking, with cow dung producing 835.12 milligrams per cubic decimeter and rabbit droppings 786.91, compared with 774.18 for poultry droppings and 723.69 for pig dung, differences the authors report as highly significant. The researchers attribute the elevated densities to the mono-specific nature of their cultures, which outperformed the multi-specific production systems described in earlier studies. Physicochemical monitoring with a multiparameter probe revealed that temperature and pH remained stable across treatments, while conductivity, total dissolved solids, and salinity were elevated in the rabbit and poultry manure ponds, likely reflecting the rich organic matter content of those fertilizers.

Nutritional analysis, however, is where the study delivers its most consequential findings. Using freeze-drying, Kjeldahl protein determination, incineration for ash content, and HPLC-based vitamin assays performed at an ISO 17025-accredited laboratory in Benin, the team quantified the bromatological profile of larvae from each fertilizer treatment. Chironomidae raised on poultry droppings contained the most crude protein at 26.80 percent, followed by rabbit droppings at 22.98 percent, pig manure at 20.48 percent, and cow dung at 17.57 percent. A correspondence factor analysis, whose two axes explained nearly 99.90 percent of the variance, cleanly separated the treatments: rabbit, poultry, and pig manure larvae clustered with protein, vitamins, organic matter, and dry matter, while cow dung larvae associated with ash, or mineral content. The larvae also carried measurable fat-soluble vitamins A, D, and E, ranging from 0.21 to 0.52 micrograms per 100 grams, and water-soluble vitamins B1 and B2 between 0.26 and 0.6 micrograms per 100 grams.

With the nutritional profiles in hand, the researchers turned to the ultimate test: feeding trials with African catfish fry. Catfish larvae were first raised on zooplankton for thirteen days post-hatching to reach fry size, starting the experiment at an average weight of just 3.06 milligrams. Fifteen circular above-ground ponds each received 150 fry, which were fed four times daily, at eight in the morning, noon, four in the afternoon, and eight in the evening, for twenty-one days. At each feeding session, one cubic decimeter of substrate was harvested from the production ponds and the live Chironomidae were collected with a 350-micrometer sieve. A control group received Coppens, a commercial imported feed. Growth and survival were monitored through control fishing every three days, with daily counts of mortalities and standard zootechnical calculations including daily weight gain, specific growth rate, survival rate, and a production index.

The survival outcomes were remarkable in their consistency. Fry fed Chironomidae from cow dung survived at 94 percent, rabbit droppings at 92 percent, poultry droppings at 95 percent, and pig dung at 95 percent, statistically indistinguishable from the 95 percent survival of the Coppens-fed control group. Final mean weights ranged from about 10.06 to 10.29 milligrams across all live-feed treatments, with the commercial feed group reaching 12.65 milligrams. The commercial diet did produce the highest daily weight gain and specific growth rate, with significant differences among treatments, and the authors attribute this edge to the superior protein content of the formulated feed. Nevertheless, specific growth rates in the live-feed groups, between roughly 25.50 and 26.90, exceeded those reported in comparable earlier studies, which the researchers link to the sheer abundance of Chironomidae available to the fry.

The implications extend well beyond the laboratory. The authors argue that Chironomidae produced from rabbit and poultry droppings, with protein contents between 22 and 26 percent plus their complement of fat- and water-soluble vitamins, can substitute for imported feed at the first feeding stage of catfish fry. This matters because the vitamins measured in the larvae fall within ranges previously associated with healthy growth in species such as grass carp, and vitamins A, D, E, and the B complex act as metabolic catalysts that support growth, immune function, and ultimately human health in consumers. For rural producers in Guinea and across West Africa, the practical message is that the raw materials for high-quality fry feed, essentially livestock manure and shallow ponds, are already on the farm, eliminating dependence on foreign currency, import logistics, and unpredictable supply chains that currently constrain the sector.

The study also carries broader ecological and economic resonance. By coupling organic fertilization with the natural productivity of pond ecosystems, the approach mirrors traditional aquaculture principles while adding modern analytical rigor: precise dosing, mono-specific larval culture, and full bromatological characterization. The researchers caution that protein values in their larvae were lower than those reported in some prior work, likely due to differences in culture media and larval age, and that the commercial feed retains an advantage in absolute growth rates. Yet the near-identical survival between live-feed and control groups addresses the most vulnerable stage of the production cycle, where losses are typically greatest. As fish demand continues to climb and wild fisheries face mounting pressure, low-tech innovations like manure-fertilized bloodworm ponds may prove that the future of sustainable aquaculture lies not only in high-tech feed mills but also in the small, wriggling insects that fish have been eating all along.

Subject of Research: Organic fertilizer-based production of Chironomidae larvae as live feed for Clarias gariepinus fry aquaculture

Article Title: Bromatological value of Chironomidae produced from organic fertilizers and their effects on the growth of Clarias gariepinus fry in the Guinean forest region

Article References: Adande, R., Djidohokpin, G., Djissou, A., Bilivogui, P., & Jean-Claude, M. (2025). Bromatological value of Chironomidae produced from organic fertilizers and their effects on the growth of Clarias gariepinus fry in the Guinean forest region. Blue Biotechnology, 2(1), Article 14. https://doi.org/10.1186/s44315-025-00024-y

Image Credits: AI Generated

DOI: 10.1186/s44315-025-00024-y

Keywords: aquaculture, Chironomidae, bloodworms, Clarias gariepinus, organic fertilizers, fish fry, live feed, Guinea, protein content, vitamins, sustainable fish farming, benthic macroinvertebrates

The “Third Water” aquaculture system represents a significant scientific breakthrough—an environment where both freshwater and seawater species coexist effectively within a controlled, closed recirculating tank. This technological innovation by OUS’s Education and Research Center for Biological Production allows for the cultivation of the Matsukawa flounder (Matsukawa-garei), a species noted for its thick, succulent flesh, complex fat profile, and naturally sweet flavor. By precisely modulating water salinity, temperature, oxygen levels, and nutrient balance, this system mimics the transitional aquatic environments flounders encounter in nature, vastly improving survival rates and growth quality.

Introduced to the public on July 25, 2023, the Matsukawa flounder was stocked initially as juveniles averaging 2.6 grams and 6 centimeters in length. The fish were nurtured meticulously in a 35-ton, fully closed recirculating tank system designed to maintain optimal growth conditions. The recirculating aquaculture system (RAS) employed here cycles water continuously through mechanical and biological filtration processes, ensuring the removal of waste products and the maintenance of pristine water quality. This allows for minimal environmental impact and resource efficiency, key components as aquaculture strives to meet rising global seafood demand sustainably.

The cultivation process spans several months, during which the Matsukawa flounder exhibit steady growth until reaching an average market weight of approximately 1.5 kilograms. The relatively rapid growth rate underscores the efficacy of the Third Water method in providing a stable and nutrient-rich environment. Moreover, the system’s closed nature provides robust biosecurity, reducing disease transmission risks and antimicrobial use compared to traditional open-sea aquaculture farms.

Recognized in culinary circles as the “King of Flounder,” Matsukawa carries prized gastronomic qualities. Its thick flesh boasts a distinct firmness paired with a luxurious layering of natural fats and subtle sweetness—a profile highly sought after in premium sushi preparation. At Kurasushi’s Osaka Expo 2025 branch, this delicacy is served as nigiri, featuring the flounder atop vinegared rice and enhanced with a soy-sauce koji marinade, a traditional fermentative dressing that complements the fish’s umami characteristics.

This commercial launch marks the second successful collaboration between OUS and Kurasushi leveraging the Third Water system. Earlier in May 2023, the market saw the introduction of “Okayama Ridai Unagi,” a similarly cultivated eel product that achieved nationwide distribution. The expansion of this innovative aquaculture branding at Kurasushi reaffirms the potential for integrated scientific research to reshape aquaculture and culinary sectors alike.

Kurasushi’s Osaka Expo 2025 branch, boasting 338 seats and an impressive 135-meter conveyor belt lane, offers patrons a diverse global menu in line with the Expo’s international cultural ethos. The integration of OUS’s Matsukawa flounder into such a high-capacity, cutting-edge venue highlights the technological and culinary prestige accreted around this new product. Early customer reactions have been overwhelmingly positive; a young Osaka local praised the fish’s perfectly balanced texture and flavor profile, bringing out its firm yet slightly crunchy flesh and elegant sweetness.

Associate Professor Toshimasa Yamamoto from OUS’s Faculty of Life Sciences, who supervises the aquaculture research, remarked on the emotional and scientific dedication behind this accomplishment. He highlighted the student researchers’ meticulous care throughout the cultivation process, likening their nurturing to raising children. Beyond mere commercial success, Yamamoto envisions the Matsukawa flounder as a symbol of Japan’s cutting-edge biological production research, aiming to attract global attention to the university’s innovative aquaculture capabilities.

The underlying science of the Third Water system entails complex hydrological and biochemical engineering challenges. Creating an aquatic milieu suitable for both freshwater and marine organisms requires precise control of ionic concentrations, osmotic pressures, and microbial communities. Advanced sensors continuously monitor physicochemical parameters, feeding data into real-time automated regulation systems to maintain steady-state conditions. This dynamic equilibrium fosters optimal metabolic rates within the flounder, enhancing growth efficiency and flesh quality.

From an environmental perspective, the recirculating aquaculture approach aligns with the broader goals of sustainable seafood production—reducing reliance on wild fish stocks, minimizing nutrient runoff, and curbing antibiotic dependence. The closed-loop system exemplifies how university-led research can translate into commercially viable, eco-conscious food sources fitting modern consumer preferences and regulatory standards.

The commercial acceptance of Matsukawa flounder also owes much to evolving consumer trends favoring traceability, welfare-conscious farming, and novel gourmet experiences. Labeling the product as “Okayama Ridai Matsukawa-garei” emphasizes regional pride and scientific pedigree, enriching the narrative behind consumers’ dining experience. This fusion of cutting-edge science with cultural appreciation may catalyze wider adoption of innovative aquaculture products in global markets.

Looking forward, OUS aims to further refine the Third Water system for additional species and explore genomic, immunological, and nutritional optimization to enhance farmed fish resilience and flavor attributes. Such multidisciplinary research integrating biology, engineering, and food science heralds a future where aquaculture can sustainably meet increasing demands without compromising quality or environmental integrity.

In summary, the commercial debut of Matsukawa flounder at Kurasushi’s flagship Osaka Expo 2025 branch represents a landmark integration of innovative aquaculture technology with culinary excellence. The union of OUS’s Third Water system and a major sushi chain not only offers consumers an extraordinary dining experience but also showcases Japan’s leadership in scientific aquaculture research. This progress underscores the transformative potential of university-industry collaboration in crafting sustainable, premium food solutions designed for the future.

Subject of Research: Innovative aquaculture of Matsukawa flounder using the Third Water recirculating system at Okayama University of Science.

Article Title: Okayama University of Science Launches Premium “Okayama Ridai Matsukawa-garei” Cultivated Flounder at Kurasushi Osaka Expo 2025 Branch

News Publication Date: July 25, 2023

Web References:
https://mediasvc.eurekalert.org/Api/v1/Multimedia/ff7bcb8d-966f-44d1-a875-eb735c92f161/Rendition/low-res/Content/Public

Image Credits: Okayama University of Science

Keywords: Matsukawa flounder, Third Water aquaculture, recirculating aquaculture system, sustainable seafood, Okayama University of Science, Kurasushi, Osaka Expo 2025, premium sushi, aquaculture innovation, biological production, closed-loop system, gourmet aquaculture