THE FRESH-WATER AQUARIUM 
11 
large tank, and see if, from the oxygen of these infusorial animalculae 
alone, life could be sustained. 
It must be the aim of him who wishes to establish an aquarium to see 
that this balance of plants and fishes is effected, for it is indispensable. 
Starting then with some idea of what we wish to accomplish, the first 
inquiry is about the kind of tank we are to use. This is an affair of more 
than mere fancy, convenience, or economy, for it is important for the 
growth of many plants that they should have the greatest amount of light 
possible, and this is especially true with fresh-water plants; so that 
where a wash-bowl or a tub would make an excellent tank for a salt-water 
collection, the same might fail of success in one with fresh-water. Be¬ 
sides, there are many specimens which we wish to examine sidewise, and 
obtain that view which is not possible to have in nature, namely, that of 
a vertical section of a pond. The requirements of a good vessel or tank 
for an aquarial collection are strength and sufficient transparency; these 
we have in a moderate degree in the inverted bell-glasses, or cake covers, 
of confectioners. If, however, the glass becomes cracked and broken 
from any cause, and it is surprising how easily it is broken, the whole 
collection of specimens is in great danger of being lost, especially if the 
accident happens in the night-time. Another disadvantage which the cake 
covers' have is, that through them the specimens are sometimes magnified, 
and irregularly too, so that whit has been put into the tank as a very 
small and finely shaped fish, in an instant becomes a giant more or less 
deformed. This kind of tank is the usual one adopted by those who are 
making an aquarial collection for the first time, and it answers many pur¬ 
poses admirably; it is sufficiently transparent, moderately strong, and 
quite cheap. One having «a diameter of twelve and a half inches, with a 
depth of eight inches, and of good thickness, can be bought for two 
dollars and a half; the knob on the top will prevent it standing steadily, 
and to obviate this difficulty a stand can easily be turned from a block of 
wood, with a hole cut in the centre large enough to admit the knob, and 
allow the bottom of the glass to rest upon it as a support. If properly 
taken care of, a tank of this sort will last for years, and be a great com¬ 
fort to its possessor, but an untimely accident will before long induce him 
to try something more substantial. 
Perhaps the best tank for the aquarium in use is what is called a rec¬ 
tangular tank, having the four sides of glass, and the base of some hard 
material such as stone, iron or wood. The glass is held in place, and 
supported at the four corners by as many pillars of iron or wood, which 
