Cuapter VII. 
THE TANK. 
When we have chosen a place for the aquarium, the next 
step is to secure a tank. This may be any water-tight vessel, 
the material of which will not alter the qualities of the water 
by impregnating it with anything that would stain it or give it 
an offensive odor, either of which would be detrimental to the 
health of the fish. 
The shape of such a vessel is usually determined by the 
requirements of the duty it is expected to perform, and should 
not, therefore, be wider at the top than at the bottom, for then 
the fish would leap out; neither should it be too narrow at the 
upper part, for this would exclude the atmospheric air bya re- 
duction of the water surface. The old-fashioned fish globe is 
about the worst vessel that can be selected for the keeping of 
goldfish as pets; it will do well enough for a temporary dis- 
play of the fish, but for permanent use it will not answer. 
However, it is not at all necessary to buy an expensive 
tank of a dealer; on the contrary, it affords so much more 
pleasure and satisfaction when one has made his own tank. 
Of the different shapes used for an aquarium tank I find 
the rectangular shape the best for all around purposes. Its 
advantages over the round, the triangular and the hexagonal 
shape are so apparent that any of the latter should only be 
constructed for special purposes. 
39 
