order
to get rid of the soluble vegetable matter, and promotes the growth of
Confervae, and other low forms of vegetation, which are obnoxious.

Aquatic plants of all kinds have been found to root freely and flourish
in pebbles alone, if their roots be covered. The plants should be
carefully cleared of all dead parts; the roots attached to a small
stone, or laid on the bottom and covered with a layer of pebbles and
sand.

The bottom being planted, the water may be introduced through a
watering-pot, or poured against the side of the tank, so as to avoid any
violent agitation of the bottom. The water should be pure and bright.
River-water is best; spring-water will do, but must be softened by the
plants for some days before the fishes are put in.

Sunshine is good for the tank at all seasons of the year. The
fresh- requires more than the salt-water aquarium. The amount of
oxygen given off by the plants, and hence their growth and the
sprightliness of the fishes, are very much increased while the sun
is shining on them.

In selecting plants for the aquarium some regard is to be paid to the
amount of oxygen they will evolve, and to their hardiness, as well as to
their beauty. When it is desired to introduce the fishes without waiting
long for the plants to get settled and to have given off a good supply
of oxygen, there is no plant more useful than the _Callitricke_, or
Brook Star-wort. It is necessary to get a good supply, and pick off the
green heads, with four or six inches only of stem; wash them clean,
and throw them into the tank, without planting. They spread over the
surface, forming a rich green ceiling, grow freely, and last for months.
They are continually throwing out new roots and shoots, and create
abundance of oxygen. Whenever desired, they can be got rid of by simply
lifting them out.

The _Vallisneria_, or Tape-Grass, common in all our ponds, is essential
to every fresh-water tank. It must be grown as a bottom-plant, and
flourishes only when rooted. The _Nitella_ is another pleasing variety.
The _Ranunculus aquatilis_, or Water-Crowfoot, is to be found in almost
every pond in bloom by the middle of May, and continues so into the
autumn. It is of the buttercup family, and may be known as a white
buttercup with a yellow centre. The floating leaves are fleshy; the
lower ones finely cut. It must be very carefully washed, and planted
from a good joint, allowing length enough of stem to reach the surface.