14 Fresh Water Aquarium 



tain plants do require these soils. But as we 

 have a number of excellent plants which suc- 

 ceed very well in pure gravel, without any 

 organic admixture, it is not advisable to use 

 any of the other mentioned mixtures for the 

 bottom covering, as they contain a very high 

 percentage of vegetable substance, which, 

 under the influence of moisture, will rapidly 

 decay, making the water more or less im- 

 pure. The fact that the water seems clear, 

 by no means guarantees its purity. Decay- 

 ing substances settle on the bottom, and the 

 moving of the inmates of the aquarium stirs 

 them up, making the water cloudy and unfit 

 for many of the tender and sensitive fishes. 

 Even a layer of gravel spread over the soil 

 is no protection against the infection of the 

 water. It may be added that the cleaning 

 of an aquarium, the bottom of which has 

 been covered with soil, is a very unpleasant, 

 and not at all easy task. 



Thus the cleanest and most satisfactory 

 material for the bottom covering is a layer 



