WHERE TO PLACE THE AQUARIUM. 
95 
changed ; for they exhaust the oxygen from the small supply of water in 
the bowl, and there is nothing to revivify the water from which they have 
extracted what is to them an indispensable element of life. The introduc¬ 
tion of plant-growth, however, alters all this; the plants give out the neces¬ 
sary oxygen, while some of the animals, on their part, repay the obligation 
by feeding on any of the vegetable matter that begins to decay, and cause 
turbidity in the water. Thus a balance is maintained, the vegetable and 
animal inhabitants of the little glass world being equally and mutually 
necessary to each other’s well-being. A few sea-snails, or periwinkles, for 
a salt water, and half a dozen pond-snails for a fresh-water aquarium, are 
the best scavengers in the world; and the best of it is, they keep them¬ 
selves, without putting their owner to any expense whatever. 
THE CASE, OR TANK. 
The aquarium is made properly of two materials. The bottom and ends 
should be made of marble or slate, and the two sides of glass—though for 
fresh-water aquaria all the sides may be made of glass, set in iron pillars, if 
the latter be enamelled. "We prefer the former method. The end-pieces have 
grooves cut in them to receive the plate glass, which is then cemented, and 
made water-tight. There are similar grooves in the bottom. The cement 
should be such as will not decompose and taint the water. The tank, if 
you are near a large city, can be bought cheaper than you can make it. 
Having bought your tank, see that the cement or putty it may contain is 
perfectly dry. Cleanse it thoroughly by filling it with successive changes 
of water. It is useless introducing any specimen until the water in the 
tank remains perfectly free from any impurity, contracted from the vessel in 
which it is placed. 
WHERE TO PLACE THE AQUARIUM. 
This is a very important point, and one which should be very carefully 
attended to—the object being to imitate, in the artificial pool of water, as 
closely as possible, the position of a natural pond, or sea. The first thing to 
remember is, that light is necessary for the exhalation of oxygen ; but that 
the light must fall as it would on a real pool of water— i. e., nefer laterally, 
or from the side, but always from the top. The aquarium should, therefore, be 
placed in a position where it may receive plenty of sunlight, tempered, how¬ 
ever, by the shade of over-hanging plants, or by a screen during the hottest 
hours of the day; for should the water become thoroughly warm, a great mor¬ 
tality among the inhabitants is almost certain to ensue. For this reason, many 
aquaria are made with a slab of slate on the side where the sunlight, if un¬ 
checked, would strike sideways through the water; when this is not done, a 
thick curtain of green baize, or some other impervious material, will answer 
the purpose. Do not place the aquarium in any place where it is likely to bo 
moved, or shaken, in closing shutters, or similar operations; a grand point 
towards success is that, once fixed, it should remain entirely undisturbed. 
