MANAGEMENT OP THE AQUARIUM. 43 



the sand ought never to be neglected, for withont i.t some 

 decaying matter, either vegetable or animal, wiU certainly be 

 present, and in time corrupt the water of the tank, and so 

 cause injury to its inmates. 



This clean sand should now be placed in the aquarium to 

 a depth of from 2in. to 4in., according to the size of the tank 

 and the character of the plants which are to be introduced. 

 But if the aquarium is bell-shaped, all its lower portion may 

 with advantage be filled with sand until it reaches that part 

 of the vessel where the sides begin to be vertical. This will 

 both lessen the depth of water and increase the rooting-space 

 for vegetation. Over the sand a layer of some fine gravel 

 should be put, which also must be washed perfectly clean. 

 This gravel may be obtained from a river or stream, but that 

 which has been sifted from the bird-sand wiU do very well. 

 The gravel is chiefly for the purpose of preventing fish and 

 their comrades from turning up the sand and sediment, and 

 thus interfering with the clearness of the water. Charcoal 

 is sometimes buried in the sand — ^for it has the power to some 

 extent of counteracting putrefaction and preventing unpleasant 

 smells. Its presence, however, in the aquarium has its draw- 

 backs : if allowed to float in the water, it will look unsightly ; 

 and if sunk in the sand, there will be a difficulty in renewing 

 it when its efficiency as a deodoriser has gone. A properly- 

 stocked aquarium needs no charcoal. 



Among the occupants of an aquarium there will be some 

 which will not care to remain in the water always ; and for their 

 accommodation it will be advisable to erect a kind of rockwork, 

 the top of which ought to rise above the surface of the water. 

 This rockwork will also provide shade for the fish and the other 

 animals which delight in retirement. It can be bought all ready 

 for the aquarium ; but often that which is offered for sale is 

 gaudily coloured, or is in other respects unsiiitable. Sometimes 

 it will be found made in the shape of ruins of various kinds. 

 Of course such rockwork is altogether out of place in a well- 

 arranged tank, for no one with any taste at all would care to see 

 a fish, for instance, swimming through the window of a house, 

 or a triton wriggling through the loophole of a castle. 



