22 



MAINTAINING FISHES 



BIOLOGICAL POLLUTANTS: Any Organism, plant 

 or animal, which is brought in with the water might 

 be considered a pollutant. In some cases, these organ- 

 isms can prove to be a nuisance. Well water is least 

 apt to contain biological pollutants. Tap water is free 

 of most biological contaminants. Lake and stream wa- 

 ter will contain various organisms and should be fil- 

 tered. The sand filter recommended for silt removal 

 will also remove most biological pollutants. If a sand 

 filter is not required wild fish and many other con- 

 taminants can be removed by a screen type filter 

 (Figure 3). 



/LOAT SWITCH FOR PUMP SUPPLY 

 OR FIjOAT valve FOR GRAVITY "SUPPLY. 



filter bag op 

 Saran screen 



52 X 52 MESH 

 O.OOa YARN 



CONCRETE TAN 



3. Screen filter for removal of fishes and other larger 

 hiotic pollutants. 



CHOICE OF pipe: The type of pipe (gal- 

 vanized, copper, or plastic) to be used for the water 

 supply leaves room for debate. New copper and gal- 



