TEOPICAL AQUARIUM FISHES 111 



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 liberator, and is carried to the bottom 

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

 somewhat horizontally across the aquarium. If the aquarium is very deep 

 (3 to 5 feet), the liberator pipe should extend about 8 inches above the 

 surface of the aquarium. Otherwise the air in the column of water in 

 the liberator pipe would make it so light that it would back up instead 

 of discharging in the bottom of the aquarium. In shallower aquaria the 

 liberator 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 heavy specific gravity of marine 

 w^ater enables us to break up the air finer than in fresh water. 



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 w^hole. 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 resisting 

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

 the aquarium. Something less expensive, but quite satisfactory for large 

 work, is wooden pipe. Quantities of this piping are used in the marine 

 division at the Philadelphia Public Aquarium, with perfectly satisfactory 

 results. For the aquarian, 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 Aqua- 

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

 bell-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. 



In using metal-framed aquaria a narrow strip of glass should be 

 placed over the cement in the corners. A recent improvement is a glass 

 rod of suitable diameter, say about one-quarter inch. This can be pressed 

 in all the way to the glass and the surplus cement wiped away, making a 

 substantial, quick and neat result. The disadvantage of glass strips is 

 that no thin glass is straight, the bend always making an unsatisfactory 

 job. 



