indefinite period without the necessity of 
being changed is a possibility easily realized. 
An aquarium of that kind is known as a 
balanced aquarium and is the result of 
establishing an equilibrium of certain nat- 
ural forces. 
In stocking an aquarium it is necessary 
to allow at least a certain amount of water 
for each fish, to plant in the sand enough 
growing water plants to furnish as much 
oxygen as the fish will require, and to add 
enough tadpoles or snails to devour the 
accumulation of waste matters, dead leaves 
and green scums. Such an aquarium will 
grow more beautiful week by weelx until it 
becomes like one of nature’s limpid pools, 
and will need only an occasional cleaning 
of the glass sides and pebbly bottom, a reg- 
ular supply of fish food, and an addition of 
as much water as evaporates. Such a dupli- 
ot 
fishes and plants affords problems that tax 
cation of the natural home conditions 
the skill of the most intelligent, and so 
makes the aquarium a source of interest to 
old as well as young. Many aquarists find 
as much enjoyment in the water plants as 
in the fishes, and take great delight in 
learning how to grow scores of beautiful 
and interesting plants, and in getting them 
to grow in artistic and effective display, 
even as is done with land plants by land- 
scape gardeners. 
While the goldfish holds the center of 
the stage in public display, it is not by any 
means the only available aquarium fish. 
Interesting and beautiful as goldfishes are, 
there are many other aquarium fishes, some 
far more beautiful, many more interesting, 
most of them more suitable for the home 
aquarium. 
Most of these fishes are tropical and 
have been imported into Germany, where 
they have become acclimated to aquarium 
conditions. Unfortunately most of them 
have as yet no common names, and so it 
will be necessary to employ their rather 
forbidding scientific names. These fishes, 
of which mention is to be made, are par- 
ticularly. suitable for the home aquarium, 
first, because they are small fishes and so 
more contented with narrow quarters; 
secondly, because they display most won- 
derful colorations, often bizarre, frequently 
changeable, according to the emotions of 
fear, anger or love; thirdly, because they 
exhibit the most unusual and interesting 
habits, especially those concerned with 
their nest building and brooding, and, 
lastly, because most of them will breed and 
raise their young in the ordinary home 
aquarium. This ability and willingness to 
breed in the aquarium endears these little 
fishes to fish lovers, for there is a genuine 
satisfaction and pride in successfully 
bringing these tiny water babies through the 
vicissitudes of life to the full perfection 
of their grace and beauty. 
In order to present these fishes. more 
readily to the mind’s eye they will be de- 
in 
of 
breathers which can breathe the oxygen in 
the 
which can breathe either the oxygen in the 
As to their 
methods of reproduction there are ovipar- 
seribed groups. According to their 
method breathing there are 
gill- 
water, and cheek-pouch breathers 
water or that in the air itself. 
ous fishes which lay eggs, and viviparous 
fishes which give birth to fully developed 
young. As regards their breeding habits 
there are the plain spawners and the nest 
builders. Of the nest builders there are 
those that build nests in the sand or peb- 
bles, and those that construct floating nests 
made of air bubbles. Space allows of the 
mention of but a few of the many fishes 
in these several groups. 
The paradise fish (Macropodus Viridi- 
auratus) isa water and air breather, hav- 
ing besides the ustial fish gills a labyrin- 
thine pouch in each cheek by means of 
which it can utilize the air above whenever 
the natural supply in the water gives out. 
These air breathing pouches make it pos- 
sible for the fish to be revived hours after 
it has accidentally leaped out of the aqua- 
rium onto the floor and become so dry and 
