11 INSTALLATIONS FOR REARING ANIMALS AND FATTENING ANIMALS, ESPECIALLY FOR REARING FISH AND FATTENING FISH AND COMPONENT PARTS THEREOF-NAMELY, FISH TANKS, FILTER TANKS, CONNECTING PIPES AND PUMPS, PREPARATION/CONDITIONING TANKS, CIRCULATING HOLLOW BODIES FILLED WITH FIBROUS MATERIAL, INTERCHANGEABLE CARTRIDGES FILLED WITH FIBROUS MATERIAL FOR SUCH HOLLOW BODIES, AND FILTRATION MATERIALS, ESPECIALLY FILTRATION GRAVEL, ALL THE AFORESAID GOODS ARE SOLD TOGETHER AS A UNIT