This post focuses on how different carbohydrate sources (sugar, jaggery, rice flour) impact water quality and shrimp growth in Biofloc Technology (BFT). This topic is ideal because it clearly explains the core scientific principle of C:N ratio manipulation in aquaculture, a concept crucial for zoology and environmental science students, while providing practical, data-backed outcomes from the thesis.
Written and reviewed by Abubakar Siddiq, MPhil Zoology (Pakistan). As a dedicated researcher and educator at Professor of Zoology, Abubakar specializes in translating complex academic studies into accessible, practical knowledge for students and aspiring scientists in aquatic biology.
Last Updated: October 10, 2025
Estimated Reading Time: ~9 minutes
Modern aquaculture faces a critical challenge: how to intensify production without harming the environment. For shrimp farmers, managing toxic ammonia waste is a daily battle that dictates the success or failure of a crop.
This is where Biofloc Technology (BFT) offers a revolutionary solution. But this eco-friendly system hinges on one simple ingredient: carbohydrates. This article dives into a doctoral thesis to explore how different carbohydrate sources—sugar, jaggery, and rice flour—dramatically influence the health and growth of Pacific whiteleg shrimp (Litopenaeus vannamei).
- What You’ll Learn: The core principles of Biofloc Technology (BFT) and the critical role of the Carbon-to-Nitrogen (C:N) ratio.
- Key Finding: While all tested carbohydrates effectively controlled toxic ammonia, jaggery showed a surprising edge in improving shrimp weight gain and survival.
- The Science Explained: How adding simple sugars or complex starches fuels beneficial bacteria that purify water and become a food source.
- Practical Application: Understand why choosing the right carbohydrate is a cost-effective strategy for sustainable shrimp farming.
Introduction
Have you ever wondered how we can farm more seafood with less water and waste? In traditional shrimp farming, only about 25% of the nutrients from feed are converted into shrimp biomass, while the rest becomes toxic ammonia (Total Ammonia-Nitrogen or TAN) in the water (p. 8). This pollution limits stocking densities and often requires massive water exchanges, posing a biosecurity risk.
Biofloc Technology (BFT) flips this problem on its head by turning waste into a resource. This post, based on M. Raghu Ram’s doctoral research, will explore the science behind BFT and reveal which common carbohydrate source works best to create a thriving, sustainable shrimp nursery.
What is Biofloc Technology and Why is the C:N Ratio Crucial?
Biofloc Technology is an innovative aquaculture system that relies on minimal or zero water exchange. Instead of flushing out waste, it encourages the growth of a microbial community—the “biofloc”—right inside the culture tank.
“Bio-floc Technology is defined as ‘macro-aggregates – diatoms, macro-algae, fecal pellets, exoskeleton, remains of dead organisms, bacteria, protozoans and invertebrates’.” (p. 5)
The magic of BFT lies in managing the Carbon-to-Nitrogen (C:N) ratio. Shrimp excrete nitrogen-rich waste (ammonia). By adding a carbon source (carbohydrates), we provide food for heterotrophic bacteria.
These bacteria consume the toxic ammonia to build their own cells, effectively locking up the nitrogen. This process not only cleans the water but also creates protein-rich microbial flocs that the shrimp can eat, reducing feed costs and waste.
Student Note: Think of it as composting in water. Just as you add “browns” (carbon) to your “greens” (nitrogen) in a compost pile, BFT adds carbohydrates to balance the nitrogenous waste from shrimp, creating a healthy, self-sustaining ecosystem.
The Experiment: Comparing Carbohydrate Sources in a Biofloc System
The study by M. Raghu Ram aimed to find the most effective and practical carbohydrate source for managing a biofloc nursery for L. vannamei post-larvae (PL). The experiment tested three readily available carbohydrates:
- Sugar (Sucrose): A simple, rapidly dissolving carbohydrate.
- Jaggery: An unrefined sugar rich in minerals.
- Rice Flour: A complex carbohydrate (starch) that degrades more slowly.
For 21 days, shrimp post-larvae were raised in experimental tanks where one of these carbohydrates was added to maintain the C:N ratio, alongside a control group with no carbohydrate addition. Researchers monitored both water quality parameters and shrimp growth metrics to determine the impact of each source.
Lab Implication: When setting up a BFT experiment, the choice of carbohydrate directly influences the speed of microbial response. Simple sugars like sucrose will trigger a faster reduction in ammonia compared to complex starches like rice flour, which provide a slower, more sustained carbon release.
Impact on Water Quality: How Carbohydrates Control Ammonia
The primary goal of adding carbohydrates is to control toxic Total Ammonia-Nitrogen (TAN). The results of this study were clear and significant.
“The average TAN values were equal in all experimental tanks (0.54 ± 0.21mg/L) but it was high (0.72 ± 0.34mg/L) in control tank. The difference in TAN levels between experimental and control tanks were significant.” (p. 37)
This finding confirms that all three carbohydrate sources were highly effective at stimulating heterotrophic bacteria to consume ammonia, keeping the water safe for the shrimp. In the control tanks without added carbon, ammonia levels continued to rise, reaching a toxic 1.15 mg/L by the end of the experiment (p. 91). In contrast, the biofloc tanks saw TAN levels peak and then decline as the microbial community matured.
Exam Tip: In an exam, if asked about the nitrogen cycle in BFT, remember this sequence: Carbohydrate addition → Heterotrophic bacteria bloom → Ammonia (TAN) consumption → Microbial protein synthesis (biofloc) → Improved water quality.
Summary of Key Water Quality and Growth Parameters
| Parameter | Biofloc Tanks (Average) | Control Tank (No Carbs) | Significance |
|---|---|---|---|
| Average TAN (mg/L) | 0.54 | 0.72 | Significant (p < 0.05) |
| Survival Rate (%, 21 days) | ~88.2% (Jaggery was highest at 89.3%) | 84.5% | Significant (p < 0.05) |
| Mean Weight Gain (g, 21 days) | ~0.337g (Jaggery was highest) | 0.324g | Significant (p < 0.05) |
| Feed Conversion Ratio (FCR) | 1.13 – 1.14 | 1.20 | Significant (Lower is better) |
Data summarized from Table-12 (p. 46).
Effects of Carbohydrate Sources on Shrimp Growth & Survival
Beyond water quality, the choice of carbohydrate had a direct impact on the shrimp themselves. The biofloc acts as a supplemental food source, and its nutritional quality can vary.
The study revealed a fascinating outcome: jaggery, the unrefined cane sugar, led to the best overall growth performance.
“The mean weight gain (MWG), average daily gain (ADG), specific growth rate (SGR) and survival values recorded were relatively high for the post larvae reared in J tank, fed with jaggery.” (p. 92)
Why did jaggery outperform pure sugar and rice flour? The thesis suggests this is due to its richer nutritional profile. Unlike refined sugar, “jaggery may be attributed to the minerals (Magnesium, Calcium, Potassium, Zinc, and Manganese), vitamins and antioxidants available” (p. 92). These micronutrients likely enriched the biofloc, providing a more complete supplemental diet for the shrimp, which translated into better weight gain and higher survival rates.
Furthermore, the Feed Conversion Ratio (FCR)—a measure of how efficiently feed is converted into biomass—was significantly better in all biofloc tanks (1.13-1.14) compared to the control (1.20). This demonstrates that the shrimp were actively consuming the biofloc, reducing their reliance on expensive commercial feed.
Why This Research Matters
This research provides practical, cost-effective strategies for small- and large-scale shrimp farmers. By demonstrating that inexpensive, locally available carbohydrates like jaggery and rice flour can effectively manage water quality and boost growth, it lowers the barrier to adopting sustainable BFT practices. This leads to reduced water use, lower feed costs, minimized environmental pollution, and a more biosecure farming operation, contributing to global food security.
Key Takeaways for Students
- BFT is a Waste-to-Resource System: Biofloc technology transforms harmful ammonia waste into a valuable, protein-rich food source for shrimp.
- Carbohydrates are the Fuel: Adding a carbon source is essential to manage the C:N ratio, allowing beneficial heterotrophic bacteria to outcompete ammonia-producing microbes.
- Jaggery Offers a Nutritional Advantage: While simple sugar and complex starch work well for ammonia control, the additional minerals in jaggery can lead to superior shrimp growth and survival.
- BFT Improves Efficiency: The presence of biofloc as a supplemental food source lowers the Feed Conversion Ratio (FCR), making aquaculture more economically and environmentally sustainable.
Test Your Knowledge: MCQs
- What is the primary reason for adding carbohydrates to a BFT system? a) To directly feed the shrimp.
b) To increase the water’s pH.
c) To provide a carbon source for heterotrophic bacteria to consume ammonia.
d) To color the water brown. Answer: c) The main function is to manage the C:N ratio, fueling bacteria that assimilate nitrogenous waste. - In this study, which carbohydrate source resulted in the highest mean weight gain for L. vannamei? a) Refined sugar
b) Jaggery
c) Rice flour
d) The control group Answer: b) Jaggery’s rich mineral and vitamin content likely created a more nutritious biofloc, leading to better growth performance (p. 92).
Frequently Asked Questions (FAQs)
Q1: Why is controlling ammonia (TAN) so important in shrimp farming? A: High concentrations of ammonia are toxic to shrimp, causing stress, reducing growth, and increasing susceptibility to disease, which can lead to mass mortality. BFT is an effective way to keep ammonia levels low without large water exchanges.
Q2: Does biofloc completely replace the need for commercial feed? A: No, it acts as a valuable supplemental food source. It allows farmers to reduce the amount of commercial feed and lower the protein percentage, which significantly cuts costs and improves the FCR, but it does not eliminate the need for a formulated diet.
Q3: Is BFT difficult to manage? A: BFT requires more technical skill than traditional pond farming. It needs continuous aeration to keep the flocs suspended and to meet the high oxygen demand of the microbial community. It also requires regular monitoring of water quality parameters like TAN, pH, and alkalinity.
Conclusion
The effective use of carbohydrate sources in Biofloc Technology is a cornerstone of modern, sustainable aquaculture. This research powerfully demonstrates that simple, affordable inputs like sugar, jaggery, and rice flour can successfully transform a high-waste system into a productive, eco-friendly one. For students of zoology and aquaculture, understanding this elegant microbial process offers a glimpse into the future of food production—one that is more efficient, resilient, and in harmony with natural cycles.
For more deep dives into aquaculture science, explore our section on Aquaculture research on ScienceDirect or the resources at the World Aquaculture Society.
Reviewed and edited by the Professor of Zoology editorial team. Except for direct thesis quotes, all content is original work prepared for educational purposes.
Source & Citations
- Thesis Title: Bio-floc studies on survival and growth of Pacific whiteleg shrimp, Litopenaeus vannamei (Boone, 1931) in nursery phase with different carbohydrate sources and varying stocking densities.
- Researcher: M. Raghu Ram (Raghu Ram Madabattula)
- Guide (Supervisor): Prof. U. Shameem
- University: Andhra University, Visakhapatnam
- Year of Compilation: 2019
- Excerpt Page Numbers Used: 1, 5, 8, 18, 20, 25, 37, 41, 45, 46, 49, 90, 91, 92, 93
Disclaimer: All thesis quotes remain the intellectual property of the original author. Professor of Zoology claims no credit or ownership. If you need the original PDF for academic purposes, contact us through our official channel.
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