24 



MAINTAINING FISHES 



However, the above system has some definite advan- 

 tages. It can be used for tanks containing sand, it 

 primes rapidly and its suction force can be easily ad- 

 justed. 



VALVE TO ADJUST 

 SUCTION 



WATER LEVEL 

 INOICATOR--- 



f VACUUM V 

 V CLEANER j ^ 



50-GALL0N 

 STEEL DRUM 



(^ 



RUBBER 

 GARDEN 

 HOSE 

 3/4" I.D. 



%=J 



AQUARIUM 



GATE VALVE 



4. A suction drain that may be used for both cleaning 

 and draining tanks not equipped with gravity 

 drain. 



Running-water tanks and large, still-water tanks 

 should be equipped with a gravity drain system. The 

 drain may be plugged by a riser pipe which serves as 

 an overflow. It is usually convenient to combine the 

 overflow and drain. If incoming water is colder than 

 the tank water, it will sink to the bottom and an ex- 

 change of water will be insured. More often, how- 

 ever, the incoming water is the same temperature as 

 the tank water. In this case exchange is made possible 

 by placing a larger pipe over the overflow pipe thus 

 forcing the water that overflows to rise from the bot- 

 tom of the tank (Figure 5). 



