THE FRESH-WATER AQUARIUM. 19 
quite clear, and no matter what kind be used, the washing 
must be attended to. The coarser the grit the better its 
appearance, and, therefore, I do not recommend common 
sand, I merely show that it may be used when better is 
not attainable. 
Mould has been extensively recommended as a bottom 
for tanks. I used it myself till I became convinced that it 
could be dispensed with altogether. It necessitates fre- 
quent changing of the water for at least a fortnight after 
the first stocking of the tank, in order to get rid of the 
soluble vegetable matter, which the water dissolves out of 
it, and its presence promotes the growth of conferve, and 
other low forms of aquatic vegetation, that become obnox- 
ious to the sight, and even hurtful to the health of the 
collection. I now use sand and pebbles only, and I find 
that aquatic plants of all kinds root freely and flourish in 
it, and, indeed, if pebbles only be used, they flourish just 
as well if their roots are covered. 
Planting is next to be performed. The arrangement 
of plants will depend on the shape and size of the vessel. 
Generally speaking, massive plants look best if set back 
with lighter plants before them, just the same as a painter 
sets his chestnuts and elms in mid-distance, and his lady 
birches in the fore-ground. Stratoides, Potamogeton, and 
other plants of a massive and decided character, are well 
seen through the interstices of Myriophyllums, Calli- 
triche, and such like fragile and delicate structures. The 
flowering rush makes a fine centre piece for a vase, and 
appears to good advantage when seen through an archway, 
in a tank containing rockwork. 
C2 
