SOIL FOR AQUARIA. 45 



common plant, however, if only for the sake of the 

 pretty kidney-shaped floating leaves and its brilliantly 

 white and abundant flowers. 



The best soil that can be selected for the purpose of 

 covering the bottoms of fresh-water tanks is fine river 

 sand, in which may be mixed a few small round stones. 

 All should be well washed, or they may be the means 

 of introducing into your aquarium objects you never 

 bargained for, which will upset the equilibrium you 

 so much desire to commence and maintain. A few 

 pieces of charcoal mixed with it, are serviceable in ab- 

 sorbing all decaying organic substances. These, how- 

 ever, should be removed from time to time, when it is 

 supposed they have taken up as much organic matter 

 as they can. Charcoal also prevents foul smells, and 

 generally acts as a deodoriser. Too much of it, how- 

 ever, is likely to be injurious. In fitting up an aqua- 

 rium the soil should be placed after the rockwork 

 has been constructed and the water plants rooted 

 in their concealed flower-pots. To prevent the soil 

 being washed up and the water rendered muddy, the 

 water must be poured in through the finely perforated 

 rose of an ordinary watering can. The fresh water 

 commonly used for drinking purposes will do, and this 

 is perhaps better than if obtained from a pond, where 

 there is likely to be much more diffused vegetable 

 matter. The water weeds, both potted and planted, 

 ought also to be well washed before they are trans- 

 ferred, otherwise fish, amphibian, or molluscan spawn 



