MARINE AQUARIUM PROCEDURES AND TECHNIQUES 



61 



Figure 4. — Theoretical section of a capillary 

 priming siphon flaring at both ends. 



Figure 5. — Simple siphon, poorly made (lower 

 part is too big). It is essential that the lower 

 part of the siphon is not immersed into the 

 water. 



these capillary siphons, we haA^e put into 

 effect a very simple and higlily efficient 

 safety device. In order for such a siphon 

 to be able to begin its priming action, it is 

 essential that its lower end does not reach 

 into the water, so that the water of the up- 

 per tank may ascend freely in the tube, and 

 that — aided by capillarity — the water may 

 reach the highest point of the curvature 

 before the Avater level in the upper tank 

 goes past the edges. When a system of 

 this type operates within a tank, it intro- 

 duces continuous variations of the water 

 level into it, provided, however, that the 

 supply to the tank is much smaller than 

 the output of the siphon, and that the inlet 

 of the siphon has a much larger diameter 

 than its curvature. 



We have also used a siphon the upper 

 part of which is capillary; in that case. 



the siphon no longer exercises practically 

 its priming action, and the water level in 

 the upper tank remains constant. Capil- 

 larity keeps a small quantity of water in 

 the tube of the siphon; when the supply 

 to the tank becomes weaker than the out- 

 put of the tube, this water breaks up into 

 short Avater columns Avhose distance one 

 from another becomes greater as the Avater 

 supply in the siphon becomes Aveaker. 

 This siphon practically neA^er runs dry. 



In these siphons, the current of the 

 Avater is strong, and the organisms, par- 

 ticularly the Diatoma, attach themselves 

 less rapidly there than on the permanent 

 siphons Avhere the current is Aveak. But 

 inasmuch as they serA^e as a subsidiary 

 canalization, the pipes are normally not 

 operating, so their maintenance is limited 

 to cleaning them after an occasional oper- 



