Abstract: The present invention relates to the use of alpha lipoic acid as feed additive for aquatic animals including fish and shrimp, especially for cold water fish as for example salmon, bream, bass and for warm water fish as for example carp, tilapia, catfish. More particular, this invention relates to the use of alpha lipoic acid for the improvement of the feed conversion ratio and/or daily weight gain in fish, for reducing mortality by regulating the micro flora of the gut and/or by protecting the animal against infections caused by pathogenic viruses.