102 NATURE AND THE CAMERA 



dition, dnd in order to do this avoid using any cloth 

 that leaves lint. 



The water-supply is an important factor in fish 

 work. Not only must the water be constantly re- 

 newed, but it should be kept at the correct tempera- 

 ture. Few fish will live long in water that varies 

 more than six degrees from that to which they are 

 accustomed. If the change is very gradual they do 

 not appear to feel it so much, but a sudden change 

 is usually fatal. If trout are to be photographed, it 

 is nearly always necessary to use ice, as the tempera- 

 ture should be about 42^ or 46*^ Fahrenheit. 



It is well to keep a thermometer in the part of 

 the aquarium where the fish is. With some fish this 

 is not needed, but with delicate cold-water fish it is 

 an absolute necessity. 



The easiest way to keep water constantly fresh is 

 to place a pail of fresh water either on the back 

 upper corner of the aquarium or on a convenient 

 place near by. A small rubber tube used as a syphon 

 will allow a steady stream to flow from the pail, 

 while another rubber tube placed in the aquarium, 

 with the end hanging out over the edge, will syphon 

 out an equal amount. In this way the supply will 

 be constantly changing; but even so it is advisable 

 occasionally to aerate the water by pouring some in 

 from a dipper held several feet above the surface. 



