THE FRESH WATER AQUARIUM. AY 
right, for these creatures subsist on vegetable matter 
only, and if a goodly number be thrown in, they will be 
found perpetually at work, eating the green growth 
from the sides, and thus constantly preserving an open 
prospect. 
Objections to Mollusks—In a highly ornamental tank, 
water-snails may be thought objectionable, as interfering 
somewhat with the beauty of the scene. I know the 
ardent naturalist will cry out against this remark, and 
ask me if I can find a prettier object than a Planorbis 
corneus, coiled round like a horn of plenty; or a full- 
grown Paludina with its globular hybernaculum richly 
bronzed and mottled. I tell my friend that I love the 
pretty creatures as much as he does, yet, as I write for 
everybody who wishes to keep an aquarium, I feel bound 
to consider how it is to be managed without them, if their 
absence is desired. I confess too, that I do object to 
their appearance in some cases myself, as I do also to 
beetles, and all other insects in a tank fitted up for the 
adornment of a drawing-room, however necessary they 
may be in the tank of a student. 
In the first place, Paludine and Planorbis are the 
only kinds to be trusted in a general collection of plants, 
and the last is most trustworthy of any. Lymnea are all 
fond of substantial dishes, and eat as ‘much vallisneria as 
they do of the mucuous growth. A dozen of these 
gentry will most effectually check the vegetation of the 
tank, by eating holes in the handsomest leaves of the 
Stratoides, and biting into the very heart of the Vallisneria. 
Starwort, too, they are very fond of, and soon clear the 
bottom of every fragment. Yet, the Eymnea are admir- 
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