Recently, eel recirculation systems have provoked increasing attention in intensive fish culture, especially concerning animal welfare. "Aquaculture", "Intensive Culture", and "Recirculation Systems" are often confused with each other. This study, first of all, differentiates among these terms. The economic relevance of aquaculture in the Federal Republic of Germany is demonstrated by figures. A tendency towards intensive methods can only be seen in trout and eel culture. The problems of recirculation systems are explained comprehensively. Particular emphasis is laid on the conflict between theoretical suitability of intensive fish production and the absence of commercially working systems. At present, intensive fish culture does not pose a serious animal welfare problem in Germany. However, it is necessary to define the biological requirements of fish concerning their optimal accommodation in aquaculture facilities. According to the Law for the Protection of Animals, these requirements have to be laid down in an ordinance. Only then control is possible as to whether aquaculture systems fulfill fish welfare demands.