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GOLDFISH VARIETIES AND 
of net (portion in water) should be about twelve to eighteen inches long, 
ten inches wide and ten inches deep. In constructing, allow extra 
material for space between top frame and surface of water. 
Constant Aquarium Filter. This device is for use in connection 
with the air pump referred to on page 10. It is capable of a number of 
variations, once the principle is understood. There are two columns of 
water in the tubes, one solid and one punctuated by air bubbles, thereby 
making it the lighter. This causes it to rise and therefore establish cir- 
culation as long as air is supplied. A 34-inch diameter glass surgical drain 
is shown at A. This should contain about eight small openings and be 
suspended two inches above the sand. This is connected by a short piece 
of rubber tubing to the rest of the system, which is of glass tubing from 
5/16 to 3% inch inside diameter. The dark sections represent rubber 
joints, making the system more flexible, less liable to breakage, less ex- 
pense in case of break and makes cleaning of each section easy. (The 
tubes require an annual cleaning.) Air is injected under pressure at C, 
which should be five inches above lowest point of pipes. This starts the 
flow, which is discharged into D, a small filter suspended in the corner of 
the aquarium, and just above water level. It may be made of glass, alumi- 
num, porcelain or eathenware, and should approximate in size five inches 
in diameter by two deep, the bottom having a few perforations. The best 
filtering medium in this work is absorbent cotton, which should be laid 
on a few pebbles, glass bars or bits of charcoal for good drainage. The 
force of air and the distance between C and the surface of water deter- 
mines the speed at which the water travels. The lower the point at which 
air is injected, the greater the speed. To start the system, disconnect at B, 
suck with the lips to start siphon, re-connect while water is running. After 
water in rise tube has reached aquarium level, turn on air-cock at C. This 
cock should always be closed when air is not wanted and pump not work- 
ing, in order to prevent water backing up into air pipe. All rubber joints 
should be tightly secured by wrapping with thread or narrow strips of 
electric tape. Rubber cement spread on connecting surfaces helps make a 
good job. If there is danger of glass tubes being broken it is best to use 
pipe of block tin. For salt water, use glass or lead. 
Instead of filtering at top of aquarium it is possible to pass the water 
through a big, large-necked bottle of sand at the lowest point of dip. Both 
tubes pass through a rubber cork, the dirty water being carried to bottom 
of bottle, discharged in a layer of pebbles, brought upwards through fine 
sand and taken off by rise pipe just inside of cork. The sand should not 
quite fill bottle. Cork must be securely tied down. This is a nice arrange- 
