Pond culture during the last decade has been developed more and more into an independent and important industrial branch of national economy. Its development at the same time led to a sharper division into two main fields: carp pond culture and trout culture. In spite of this the science of the entire pond industry, inclusive of artificial fish-culture as contained in this book, has remained equally important for the instruction of both the carp pond culturist and the trout grower. It will be useful for each of them to use the experiences of the other and to draw comparisons. General principles in both industrial branches are largely the same, also transitions in practice repeatedly erase the division to again form a whole: the pond industry in a larger sense. It has become self-evident today that the small pond culturist, who is concerned only with the maintenance of fish, informs himself about the breeding of his fish, and that the lake and stream fishermen will repeatedly learn from the pond culture industry. All expedients for the advancement of the pond industry and for lowering production costs, such as the care and treatment.of ponds, fish feeding, precautions for avoiding fish losses and fish diseases are more effectively and successfully applied by the care fhl consideration of the given environmental requirements of the pond fish, their nutritional demands, the regulations of natural food production in the pond, and the peculiarity of the fish diseases. I have therefore placed at the beginning of this textbook, the Biological Principles of Production which influence more than anything else the industrial procedures of the pond industry. The opposite pole is formed by the treatises on fish enemies and fish diseases which not less strongly oppose industrial success and management. In spite of this, each division of the book is complete and comprehensive in itself and independent of the others.