The Aquaculture Tank System is a great introduction to fish farming. Simple to set up and maintain, it incorporates all of the aspects of aquaculture on a smaller scale. 
The System is suitable for many species such as, tilapia, catfish and ornamentals.  This picture shows the CropKing 300 gallon aquaculture unit. The smaller tanks on the right are the bio-filters. In this system, the water is moved completely by air. No additional pumps are required for system operation.