THE FRESH WATER AQUARIUM. | 
the bottom the glass can be quickly cleaned with the aid 
of water and fine sand, or rotten-stone. 
Exhaustion of Oxygen is made manifest by the fishes 
coming to the surface to gulp air, and it is also mani- 
fested by their retiring to the bottom, and quietly extend- 
ing themselves on their backs in “ horizontal repose’ — 
the repose of death. If too many animals be crowded 
into the vessel, this will soon happen, and either the 
number must be reduced or the water must be frequently 
changed, or we must have recourse to aeration. I con- 
sider the two latter remedies a proof of the incompetency 
of the aquarian—the necessity marks very bad manage- 
ment indeed. 
Temperature.—If the aquarium be too much exposed 
to the heat of the sun in summer, or to the heat of a 
fierce fire in winter, the water will get tepid, and signals 
of distress will be shown by the protrusion of many 
panting mouths at the surface. I find that if the tem- 
| perature rises above sixty degrees, things do not go on so 
well. The use of a blind or paper screen is, therefore, 
essential in summer time. 
On winter evenings, when the room is made cozy by 
blazing blocks of coal, the collection will often show signs 
of distress. By opening the lower window-sash one or 
two inches when leaving the room for the night, things 
may be restored to a normal state in a few hours, and 
even if the weather is somewhat severe no harm will be 
done. At the same time intense cold checks the growth 
of the plants, and throws the fishes into a state of torpor, 
and the freezing of the water may cause the bursting of 
the tank. 
E2 
TS en sts SE 
