46 



C. M. BREDER, JR. 



closed, the maximum flow in the opposite 

 direction has been reached. 



If three valves are arranged on either 

 line A or line B, or such a set on both, 

 various water-treatment devices may be 

 placed in the series, such as a heating or 

 cooling device, in which case the water 

 may best be passed through a glass coil for 

 heat exchange. This arrangement could 

 equally well be used for any kind of de- 

 contamination which might be required or 

 for the introduction of specified materials 

 being mixed with the passing water. Un- 

 like most aquarium plumbing, in this case 

 the water must pass from one aquarium 

 to another, so that as many as may be 

 needed can be placed in series. 



A diagram of a more usual arrangement 

 for a closed circulating system is shown in 

 figure 8. This is the fonn which is per- 

 haps most useful for general laboratory 

 purposes. Here each aquarium is supplied 

 and drained directly from a common sup- 

 ply and return. It is advisable to use a 

 pump of somewhat greater capacity than 



needed for the purpose. With this means 

 the excess water can be returned to the 

 reservoir without passing through the 

 aquariums, which greatly assists in the 

 efficient application of whatever water 

 treatment is being given and insures ade- 

 quate pressure for the system. Simple fil- 

 ters may be made by wedging a piece of 

 glass in a small aquarium and filling the 

 intake side with suitable filter material, 

 while the reservoir may be used for what- 

 ever chemical or other treatment is to be 

 applied. Two may be provided, as shown 

 in the figure, and used alternately or to- 

 gether. A constant -level siphon takes the 

 water to the first reservoir aquarium. 

 Only one siphon is shown, which may be 

 switched to the other aquarium for clean- 

 ing purposes. 



The pipes and fittings used in this sys- 

 tem are standard hard rubber. Connec- 

 tions between aquariums at the same level 

 may be made by "jumpers" which are 

 preferably of hard rubber. Their use is 

 indicated in the lower-level aquariums 



I^iGURE 7. — Pump provided with reversible-flow device. The plastic pump here shown is powered by 

 a 1/80-hp. motor and is rated to deliver 3.7 gallons per minute at zero head. 



