Simple Sugar Dextrose Emerges as Best Carbon Source for Zero-Exchange Shrimp Hatcheries

A quiet revolution is unfolding in the tanks where the world’s shrimp begin their lives. Researchers at Acharya Nagarjuna University in Andhra Pradesh, India, have shown that the choice of an ordinary kitchen-chemistry ingredient—a simple sugar—can dramatically improve the survival of Pacific white shrimp larvae raised in water that is never exchanged. In a study published in the journal Blue Biotechnology, Kola Suneetha, P. Padmavathi, and Darwin Chatla compared three carbohydrate sources in a biofloc system and found that dextrose, a glucose sugar derived from simple starch, outperformed both fructose and lactose in keeping fragile young shrimp alive through the most vulnerable weeks of their development.

The stakes are considerable. Shrimp aquaculture has become one of the fastest-growing food production sectors on the planet, and India sits at its center. The country ranks third in global aquaculture output after China and Indonesia, accounting for 7.70 percent of world production, and its sector has posted double-digit annual growth exceeding 10 percent over the past decade. Yet the industry’s Achilles heel lies at the very start of the production line: hatcheries that supply healthy seed stock. Poor quality larvae during the initial stages constrain survival, growth, and ultimately the productivity of entire farming operations downstream.

Conventional shrimp hatcheries solve their water quality problems the old-fashioned way—by flushing. Large volumes of water are exchanged continuously to keep toxic nitrogenous wastes in check, a strategy that carries heavy costs in pumping, collection, filtration, and disinfection, while also creating pathways for disease and discharging nutrient-rich effluent into the environment. Biofloc technology, or BFT, offers a fundamentally different approach. Instead of removing nitrogenous waste, the system recruits communities of heterotrophic bacteria to convert it into microbial biomass. By manipulating the carbon-to-nitrogen ratio in the water, farmers encourage these bacteria to proliferate, forming dense suspended aggregates—the flocs—that shrimp can graze on as a natural, continuously available food source.

The catch is that bacteria need carbon to do this work, and not all carbon sources are created equal. Simple sugars such as molasses, glucose, and fructose are rapidly degraded, while complex materials like rice bran and cellulose break down slowly. The choice of carbohydrate shapes how quickly flocs form, how efficiently nutrients are assimilated, and how stable the microbial community remains. Despite the technology’s successful adoption across broodstock, nursery, and grow-out phases of shrimp production, information on its effectiveness during the delicate larval and postlarval stages of Penaeus vannamei has remained scarce—precisely the gap the Indian team set out to fill.

The experiment took place at the BKMN shrimp hatchery in Undavalli, in the Guntur district of Andhra Pradesh. The researchers used eight circular high-density polyethylene tanks of 1000 liters capacity, each with a working volume of 800 liters, meticulously cleaned and treated with bleaching powder before use. Specific pathogen-free shrimp nauplii, confirmed disease-free by PCR testing, were stocked at an extraordinarily high density of 100 larvae per liter—80,000 animals per tank—at the mysis-1 stage. Three biofloc treatments were established at a fixed carbon-to-nitrogen ratio of 15:1, using fructose, lactose, or dextrose as the carbon source, alongside a control with no carbohydrate addition. The trial ran for 13 days, until the larvae reached postlarval stage 10, with zero water exchange throughout.

Building the flocs required careful staging. Following the protocol pioneered by aquaculture researcher Yoram Avnimelech, the team introduced nitrogen on the first day by adding 1.5 grams of ammonium chloride, then added carbon sources on days three and five at 5.62 grams, doubling the dose to 11.25 grams on day seven. The water’s transformation from clear and transparent to light brown signaled that floc formation was underway. Larvae were fed a commercial microencapsulated diet with a minimum protein content of 52 percent, distributed across six daily feedings, with quantities adjusted to floc volume at each developmental stage.

The water chemistry results told a clear story. Temperature remained in the optimal 27 to 29 degrees Celsius range, and dissolved oxygen stayed between 5.30 and 6.24 milligrams per liter, comfortably above the lethal threshold of 1.0 ppm reported for the species. More striking were the differences in nitrogen compounds. Total ammonia nitrogen in the biofloc tanks ranged from 0.69 to 0.78 milligrams per liter, significantly lower than the control’s 1.07. Un-ionized ammonia, which is highly toxic to shrimp, measured just 0.12 milligrams per liter in the biofloc treatments against 0.36 in the control. Nitrite, which damages the circulatory and immune systems of aquatic animals, was a mere 0.06 milligrams per liter in the biofloc systems compared with 1.53 in the control—well above the 1.0 milligram per liter considered optimal for successful culture. Nitrate and alkalinity also differed significantly among treatments, with biofloc alkalinity of roughly 127 to 128 milligrams per liter far exceeding the control’s 91.38.

Survival data sealed the case for dextrose. At postlarval stage 1, dextrose-fed tanks achieved 93 percent survival, followed by fructose at 88.67 percent, lactose at 86.33 percent, and the control at 79.33 percent. By postlarval stages 5 and 10, the gap widened: 90.67 percent for dextrose, 85.67 percent for fructose, 78.33 percent for lactose, and a sobering 66.67 percent for the control. The researchers attribute dextrose’s advantage to its chemistry. As a monosaccharide derived from simple starch, it is readily broken down by bacteria, driving robust floc formation—the dextrose treatment produced the greatest floc volume at 1.62 milliliters per liter, compared with 1.12 for fructose and just 0.84 for lactose, a disaccharide that microbes decompose more slowly.

The broader implications extend beyond a single hatchery in coastal India. Every biofloc treatment group surpassed the 70 percent survival benchmark considered appropriate for the species and for experimental hatcheries, and the overall biofloc survival range of 71 to 86 percent dwarfed the control’s 53 percent. Because the systems operated with zero water exchange, they promise reduced water costs, enhanced biosecurity against pathogens, and a smaller environmental footprint—attributes that matter enormously as the industry confronts disease outbreaks and tightening environmental regulations. The flocs themselves add nutritional value, offering shrimp a supplementary microbial food source alongside formulated feeds.

For an industry that contributes roughly 1.24 percent to India’s gross value added and more than 7.28 percent to agricultural GVA, with exports of 12.22 million tonnes valued at 1.42 billion US dollars in 2023, even incremental gains in hatchery survival compound into substantial economic returns. The study’s conclusion is pragmatic: fertilization with dextrose at a 15:1 carbon-to-nitrogen ratio can efficiently maintain a shrimp hatchery system without any water exchange. As biofloc technology continues its march from experimental tanks to commercial operations worldwide, this finding suggests that one of the most consequential decisions a hatchery manager makes may be as simple as choosing the right sugar.

Subject of Research: Biofloc technology with different carbon sources for Pacific white shrimp hatchery production

Article Title: Hatchery performance of Pacific white shrimp, Penaeus vannamei in Biofloc technology by using different carbon sources

Article References: Suneetha, K., Padmavathi, P., & Chatla, D. (2024). Hatchery performance of Pacific white shrimp, Penaeus vannamei in Biofloc technology by using different carbon sources. Blue Biotechnology, 1(1), Article 13. https://doi.org/10.1186/s44315-024-00016-4

Image Credits: AI Generated

DOI: 10.1186/s44315-024-00016-4

Keywords: biofloc technology, Pacific white shrimp, Penaeus vannamei, aquaculture, dextrose, carbon source, water quality, larval survival, hatchery, zero water exchange, carbon-nitrogen ratio, sustainable aquaculture