140 GOLDFISH VARIETIES AND 
THE MICROSCOPE IN AQUARIUM WORK 
Aquarium work in general and fish breeding in particular can be 
made both more interesting and more successful by the use of a micro- 
scope. For most purposes a very cheap instrument is satisfactory. In 
fact, a low power lens is preferable to a high in examining 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 quantities presents a vast 
field for new study, but we are here mostly concerned with the practical 
points of raising young fish. On page 135 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 magnifying 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 
microscope the small pocket folding lens known as a “thread counter” 
will do. This costs about twenty-five cents. 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 these organisms and thus 
be apt to deceive the observer as to the actual food value contained in 
the water. Also with high magnification the field of vision and the area 
of sharp focus are smaller, while movements are apparently much more 
rapid, making observation difficult. 
The majority of the valuable organisms are rotifers. These move 
in a steady, revolving or rotating manner. On page 57 will be found 
instructions for propagating these organisms for purposes of feeding 
young fish. Most rotifers can be readily identified as such because they 
