136 MARINE AQUARIA 



inmates. The surface of the water takes up enough oxygen to maintain 

 a few animals, but if our ideas are more ambitious it will be best to install 

 an air pump, operated by electrical power. This will more than com- 

 pensate for any plant deficiency, especially if the air is liberated in very 

 small bubbles. In the case of large marine aquaria where the water is 

 constantly pumped out, filtered and returned, the oxygenating is accom- 

 plished by a very simple and, at the same time, clever device. The water 

 is discharged with some force from a small pipe into the open end of 

 another pipe just enough larger that the water discharge pipe will fit 

 loosely in it. The second pipe is the mixer, and is carried to the bottom 

 of the aquarium, where it is bent to a right-angle so as to shoot the air 

 and water somewhat horizontally across the aquarium. If the aquarium 

 is very deep (3 to 5 feet), the intake of mixer pipe should extend about 

 8 inches above the surface of the aquarium. Otherwise the air in the 

 column of water in the pipe would make it so light that it would 

 back up instead of discharging in the bottom of the aquarium. In shal- 

 lower aquaria the end of the mixer pipe will not need to stand so high 

 above water-level. By this method the air bubbles are mostly very 

 minute, producing the effect, from a little distance, of smoke. The high 

 specific gravity of marine water helps to break up the bubbles much finer 

 than in freshwater. 



Marine Aquaria. While it may not always be possible to entirely 

 avoid having metal come into contact with the water of the marine 

 aquarium, this risk should be reduced to a minimum. Copper, brass and 

 zinc are particularly dangerous. The metal now coming into use, Monel 

 metal, is not entirely free from copper, but, on the whole, is very satis- 

 factory, and has the advantage of great strength as well as a pleasing 

 light color. Marine bronze is also good and not so expensive as Monel. 

 Iron pipes and valves lined with lead are now made, especially for resist- 

 ing chemicals. These are very fine for carrying marine water to and 

 from the aquarium. For the aquarist working on a comparatively small 

 scale, lead pipe is best. 



With the all-glass aquarium we have no metal problem to contend 

 with. Aquaria of the smaller sizes are satisfactory for marine purposes 

 if not overstocked. In the executive offices of the Battery Park Aquarium 

 in New York City, they have in successful operation a number of jar 

 aquaria, one of them having continued without interruption, except for 

 change of animals, since 1900. This should give reassurance to those 

 who hesitate to establish marine aquaria. 



Lighting. Another radical difference from the freshwater aquarium 

 is that the marine aquarium requires considerably less light. When we 

 gee such intense light at the shore, it is difficult to realize that only a few 



