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Chapter Sixteen 



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 X3 



The Microscope m Aquarium \Vork 





Aquarium work in general and fish breeding in particular can 

 be made both more interesting and more successful by the use of a 

 microscope. For most purposes a very cheap instrument is satis- 

 factory. In fact, a low power lens is preferable to a high in examin- 

 ing water for infusorian food. 



All aquaria contain various beautiful and highly interesting 

 forms of microscopic life, some harmful, some negative, but mostly 

 beneficial to fishes. The constant changing of varieties and quanti- 

 ties presents a vast field for new study, but we are here mostly con- 

 cerned with the practical points of raising young fish. On page 51 

 we refer to the use of infusoria as food for young fish. To determine 

 the presence of this food, touch the tip of the finger lightly to the 

 surface of the water, preferably to the side nearest the source of 

 light. This is because they are mostly at the surface and they seek 

 the light. Place this drop on a glass slide and observe under a good 

 magnif3ing glass or a low-power microscope. The latter is rather 

 preferable, as the focus can be changed as required, and it is fitted 

 with a mirror to facilitate observation. In the absence of a micro- 

 scope the small pocket folding lens known as a "thread counter" will 

 do. In using this the frame of the counter should be laid directly on 

 the glass containing the drop of water, and the whole placed over a 

 mirror held at the proper angle to reflect light upwards, but too 

 strong a light should not be used. A little experimenting will soon 

 show the best light to work by. 



The creatures which are of value as food to newly hatched fishes 

 are generally of a size just too small to be detected by the naked eye, 

 or at most they look like specks of dust. At the same time they are 

 plainly observable under a good magnifying glass or low-power 

 microscope. There is a great deal of life in the water of a smaller, 

 size than will be shown in this way and which probably has no food 

 value to fishes. The high-power microscope would show many of 



