International Journal of Marine Science, 2025, Vol.15, No.6, 303-312 http://www.aquapublisher.com/index.php/ijms 309 al., 2024). In addition, some bacteria can produce by-products such as organic acids, enzymes and vitamins, which make the water quality and intestinal environment more conducive to the digestion and absorption of animals, and improve their appetite and nutritional status as a result. More interestingly, after these probiotics colonize in animals, they can also stimulate the immune system, increase indicators such as phagocyte activity and lysozyme levels, thereby enhancing disease resistance (Wani et al., 2025). It is precisely because of the combined effects of several aspects that probiotics have gradually become an important alternative to antibiotics, which is also relatively consistent with the direction of green breeding. 6.2 Construction of biofloc technology (BFT) and its health effects BFT may seem like a new technology, but the core idea is actually quite simple: allowing microbial communities to "work on their own" in water. By adding carbon sources to adjust the carbon-nitrogen ratio to a range suitable for the rapid reproduction of heterotrophic bacteria, the harmful ammonia nitrogen will be converted by these bacteria into their own proteins, eventually forming flocculent masses that can be consumed by animals such as prawns (Wandana et al., 2024). These flocs are not only a source of nutrients but also a key factor in maintaining water quality stability. Due to the large number of heterotrophic bacteria, toxic nitrogen in the system is not easy to accumulate, and pathogenic bacteria (especially vibrio) also find it difficult to gain an advantage in such a microecosystem. In order to keep the flocs suspended and active all the time, the BFT system usually requires strong aeration and smooth water circulation; otherwise, microbial activity will decline (Rahman et al., 2023). An environment with high dissolved oxygen and rich bacterial flora is often very beneficial for farmed animals. Not only do they grow well, but the incidence rate is also lower. It can be said that BFT accomplishes both "purifying water quality" and "providing nutrients" simultaneously through microbial ecological engineering. 6.3 Maintaining microecological diversity and water stability In healthy aquaculture, microbial diversity is often overlooked, but its role is as important as that of water quality indicators. A diverse microbial community can undertake more functions, such as organic matter degradation, nitrogen cycling, and pathogen inhibition. Once these functions are shared by different microbial communities, the system will be more "resilient" when encountering environmental changes. Like in a pond with a relatively balanced algal and bacterial structure, even if a certain type of algae suddenly decreases, other algae can replace it in time and will not cause sharp fluctuations in water quality (Canak et al., 2023). To maintain this diversity, the abuse of broad-spectrum antibacterial agents should be avoided as much as possible in daily management. Otherwise, both beneficial and harmful bacteria will be eliminated together, making the system more prone to imbalance. At the same time, different types of probiotics can be alternately administered or compound bacterial agents can be used to make the ecological structure more stable (Guo et al., 2023). In addition, the feeding of feed and the control of water quality should not be extreme either; otherwise, certain types of microorganisms may grow out of control due to overly biased conditions. Only when the micro-ecological structure remains rich and balanced can water bodies remain stable for a long time and be less likely to experience sudden deterioration or disease outbreaks. 7 Nutrition and Immune Management of Aquaculture Species 7.1 Optimization of amino acids, fatty acids, and vitamin supply In aquaculture production, feed is often regarded as a "cost", but what truly determines the physical condition of fish and shrimp is whether the nutritional ratio is in place. The amino acid part is often overlooked, especially when plant protein is used to replace fish meal. The problem of low content of essential amino acids such as lysine and methionine will be exposed. If no additional supplementation is provided, the growth of animals is likely to stagnate and their immunity will also decline. The situation of fatty acids is somewhat different. Marine fish and shrimp themselves have a high demand for omega-3 long-chain polyunsaturated fatty acids such as DHA and EPA. HUFA is not only an important component of cells, but also related to anti-inflammatory, anti-stress and other abilities (Milijasevic et al., 2024). Adding an appropriate amount of high-quality fish oil or algal oil to feed can often significantly improve the fatty acid composition in the body and enhance disease resistance. As for vitamins, although the demand seems not large, the problems that arise when lacking them are quite obvious. For example, when there is insufficient vitamin C and E, the antioxidant capacity is weak, wound healing is slow, and it is also
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