242 FISH CULTUEE 



unnecessary to change the water frequently, 

 especially if the tank be well provided with 

 suitable aquatic plants. Simply replace that 

 which has been lost through evaporation from 

 time to time. If care be exercised and the 

 aquarium kept clean, a complete change of 

 water is only necessary about once in six 

 months. It would be well to introduce at first 

 a few snails and tadpoles, and then, after two 

 or three days, the fish. 



A careful person will wash the inside of the 

 glass of a show-aquarium daily, or at least 

 thrice a week, to keep the surface free from 

 green slime, a vegetable growth (confervae) 

 which covers the glass and develops very 

 rapidly in a fairly bright light, as when the 

 aquarium is set near a window. The growth 

 of the useful plants in the tanks and of its ani- 

 mal life requires that the aquarium should get 

 considerable sunlight, but too much sunlight, 

 together with the heat of a room, may raise 

 the temperature of the water so high as to in- 

 jure the fish because of the rapid loss of oxy- 

 gen. Hence sensible care must be taken in this 

 respect. Any fish or animal that may die 



