overlooked in no instance in the construction or operation of an 

 aquarium. 



The ideal public aquarium should be equipped for the display of 

 both salt and fresh water specimens. There should also be operated 

 as an adjunct a model fish hatchery where the public may see the 

 hatching and rearing of several species of fish such as shad, white- 

 fish, pike perch, yellow perch, and other semi-buoyant eggs incubated 

 in jars, and the non-buoyant eggs of salmon and trout hatched on 

 trays in troughs. A valuable feature also in connection with a modern 

 aquarium is a public lecture hall, where popular talks may be given 

 by the director or members of the staff. A museum with certain pre- 

 served aquatic specimens is also advisable. And still again, the main- 

 tenance of balanced or self-sustaining aquariums adds another excel- 

 lent feature for nature study in connection with school work. 



In maintaining displays of salt water fishes it is essential to have 

 sea water. The experience of the Government with the aquarium at 

 Washington and at several expositions clearly demonstrates this. 

 Theoretically, sea water can be made of 81 parts of common salt, 7 

 parts of magnesium sulphate, 2 parts of chloride of potassium, and 10 

 parts of magnesium chloride, one pound making about three gallons. 

 But fish do not thrive in it. Sea water, however, may be brought to 

 the aquarium in tank cars and stored in reservoirs. It should be 

 carefully filtered and may be used over and over again in a closed 

 circulation. There should be one reservoir in reserve so that the water 

 may "rest," or recuperate, as it were. It should be filtered each time 

 before use. All water whether fresh or salt should be regularly fil- 

 tered in public aquariums. Impurities which may be deleterious to 

 fish life are thus removed and turbidity affecting clear display is 

 avoided. 



Since cleanliness is of prime importance, each aquarium should be 

 cleaned on alternate days. On the days when not cleaned, feeding 

 should occur. This plan has been adopted after many years of exper- 

 imentation at Washington. One exception is the case of aquariums 

 containing sea horses. These interesting fishes feed chiefly on Gam- 

 marus, which small form of life does not reproduce rapidly if the 

 aquarium is disturbed frequently. 



The food of fishes, reptiles, and aquatic mammals in captivity 

 usually consists of chopped meat, clams, mussels, shrimps and small 

 fish. It is essential in feeding not to be too generous ; overfeeding 

 is far worse than underfeeding. Surplus food should not be allowed 

 to foul the bottom. 



Temperature rules must be carefully observed. Tropical salt 



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