What methods are there to treat off-flavor (muddy taste) in eel farming?

The muddy taste of eel is similar to that of other freshwater farmed fish. Its cause is mainly that chemical substances produced during the growth and reproduction of algae such as Oscillatoria and Anabaena in the aquaculture water, and of actinomycetes among bacteria, are released and dissolved in the water, then penetrate into the eel's muscle, causing the eel to develop a distinctive muddy taste.

In eel farming in earthen ponds, algae are used to maintain the ecological environment of the pond water, consume organic matter in the water and some chemical substances harmful to eels, and reduce the amount of water exchange, which helps the normal growth of eels. However, under suitable water temperature conditions and an environment rich in organic matter, algae will rapidly reproduce and grow, producing large amounts of chemical substances. Pond bottom silt, the large amount of fecal secretions produced by eels, and lost residual feed provide good nutritional conditions for algal reproduction and growth. In seasons with higher water temperatures, algae reproduce in large quantities, and even increasing the amount of water exchange makes it difficult to control the stability of algal numbers. Earthen ponds and large-area intensive culture ponds have the conditions required for the growth and reproduction of algae and actinomycetes. The chemical substances produced by algae and others that cause the muddy taste of eels remain at a certain concentration in the aquaculture water for a long time, so the eels produced are prone to developing a muddy taste, especially during the high-temperature period from July to October.

How can the muddy taste of eels be effectively prevented in aquaculture production? Controlling the bottom substrate of the pond, reducing the silt content at the pond bottom, and reducing the sources of organic matter in the water during the farming process are key. After a farming cycle ends, the pond should be dried and the pond bottom exposed to the sun, and the silt at the pond bottom should be removed from the culture pond. During the farming process, the organic matter content of the water should be controlled; a water source with low organic matter content should be selected; the amount of water exchange should be increased; water quality improvers such as quicklime, zeolite powder, ion exchange and complexing agents, and oxidants should be used regularly; and the use of microecological preparations has unique advantages in stabilizing the algal phase, cultivating water color, and inhibiting the growth and reproduction of actinomycetes, Oscillatoria, and Anabaena. It can also use the highly selective ion exchange capacity of its molecular active groups to achieve the effect of regulating and improving the substrate. Regular use of microecological preparations can avoid the many troubles and inconveniences caused by disinfection due to large water exchanges, reduced fish food intake, and so on. It is economical and quick, and can fundamentally eliminate the occurrence of muddy taste.

Eels that already have a muddy taste can have it removed after being held in clean flowing water; at the same time, the combined use of seaweed extract and similar products can achieve the dual effect of improving flesh quality and eliminating muddy taste. In short, only by regularly using microecological preparations to regulate water quality and adding seaweed extract to the feed can the occurrence of muddy taste be effectively prevented.