THE AQUARIUM AND WATER PLANTS. 277 



this aeration takes place ; the oxygen of the water is 

 exhausted, the plants become diseased, and the aquarium 

 is a failure. The difficulty is, to give sufficient light, 

 without affording too much. 



Occasional sunshine, if gentle, is essential, but if the 

 water becomes heated, the vegetation will be injured and 

 the animal life be destroyed. A shade, sufficient to admit 

 the light, but to retard the fierce rays of the sun, will be 

 beneficial. 



Ground glass, or oiled paper, may be used ; in fact, 

 any thing that will admit light without heat. 



Suppose we have constructed our aquarium. The bot- 

 tom may be formed of loam and sand, or of small pebbles 

 and sand, in which almost any aquatic plant will flourish. 



In planting, remove a few pebbles, lay out the roots, and, 

 by replacing the pebbles, hold them in their place. 



For ordinary tanks, almost any of the common aquatic 

 plants found in brooks or ponds will be suitable. 



It is an interesting fact, that the coarsest plants soon 

 adapt themselves to circumstances, and that their growth 

 becomes more delicate. The common Pond weed (Pota- 

 mogeton) appears too rank a plant for an aquarium, 

 but in less than a month its character becomes changed ; 

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