CONDITIONS OF LIGHT 



As elsewhere stated, the best light for the aquarium is either a 

 northern or northeastern exposure during the summer, and a position 

 where it may receive a good, unobstructed light during the winter, when a 

 few hours of the morning sun would be beneficial, A fine growth of plants 

 is the best indication of favorable conditions, for when the light is excessive 

 at noon or during the early afternoon, it will not only cause a loss of the 

 suspended oxygen by a marked increase in the temperature of the water, 

 but also affect the growth of the plants by a scorching and decay of the 

 leaves, and arrestment of their' growth. Too little light is also detri- 

 mental because plants require good light to grow. 



When the admission of light is principally on the surface of the water, 

 the conditions are nearest perfect. The plants will grow vigorously and 

 the animal inmates be the m,ost comfortable. For this reason aquaria 

 exposed to very strong side light should be provided with a screen for use 

 during the heated portion of the day. This may be constructed of one 

 or more thicknesses of violet or greenish tissue paper or cheese cloth, 

 attached to a light rod, to be bung over the front pane of glass. Window 

 shades partly lowered or raised from below, or the setting of the aquarium 

 back from the window are also effective measures. 



Wooden tanks only admit light on the surface and should be placed 

 where they will get the benefit of the morning sunlight or provided with 

 awnings or other coverings that may be used when the heat of the sun is 

 excessive. A fine growth of plants with floating leaves is the best screen 

 to arrest the sunlight, and for this purpose lilies and water-poppies are 

 used. 



A little experience will teach the aquariist when the conditions are the 

 most favorable, and his ingenuity will devise methods of reaching the best 

 results. 



WATER CONDITIONS 



The oxygen necessary to sustain the life of fishes is not that which 

 forms a chemical constituent of water (HgO) but that contained in the air 

 dissolved or held in suspension in the water. How considerable this is 

 may be realized by looking through a glass of water heated near the boil- 

 ing point. 



In streams or ponds, aeration is maintained by the action of the wind 

 on the surface, but in aquaria this condition is absent, and if air is not 



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