Effects of selected water quality variables on the persistence of tannic acid and related compounds under simulated aquaculture conditions

Tannins have potential commercial applications in aquaculture for the preve ntion of piscine diseases and off-flavor in fish. Selected water quality va riables, such as temperature, pH, dissolved oxygen, light intensity, total hardness and total alkalinity, and available nutrients found in fish ponds were examined for their influence on the fate of gallic acid, methyl gallat e, propyl gallate, and tannic acid. It was determined that total hardness a nd alkalinity were the most effective factors in the dissipation of tannin compounds. High levels of selected water quality variables were significant ly different from low levels in their ability to transform tannin compounds . It was also found that natural suspended solids were effective in precipi tating 60% of the methyl gallate and 81.3% of the propyl gallate per week f rom solution. Abiotic processes, such as physical transportation and chemic al transformation, affected the fate of tannin compounds in a simulated fis h pond. This study may guide the use of tannins as a feed additive or disea se treatment in the management of fish-farming problems.