280 BULLETIN OF THE UNITED STATES FISH COMMISSION. 
in the water. The water may be re aerated by the use of a syringe or 
by dipping it out and pouring it back. The probability is that a small 
quantity dipped out and replaced with an equal amount of fresh cold 
water will be all that is necessary. Where the water is completely re- 
newed it should be about the same temperature as the old. Fish are 
often killed or become diseased by being plunged from water of the 
temperature of an ordinary living room into water icy cold. Their gills 
(lungs) become congested, which produces inflammation and ulceration, 
and they show all the appearance of tuberculous diseases. The smaller 
the aquarium the more likely it is to be affected by either internal or 
external influences. The changes of temperature particularly will be 
more rapid. As before stated, if given proper conditions and not over 
stocked with animal life, such disturbances very rarely occur and onl^ 
from accidental causes, such as are always occurring in all the affairs 
of life. 
The ordinary cleansing of the aquarium consists in the cleaning of the 
glass and the removal of sediment, which latter is easily and efficiently 
accomplished by the use of a siphon or a pipette, also called lifting tube. 
This is simply a glass tube drawn in a little at both ends for conven- 
ience in using. This is used by holding the forefinger over the open 
ing in the top of the tube and directing the other end over any sedi- 
ment to be removed. The finger is then removed from the top of the 
tube when the air escaping the water will rush into the tube, carrying 
the sediment with it. By again placing the finger over the opening in 
the top of the tube it can be lifted out with its contents and emptied 
into some vessel by withdrawing the finger from the opening. 
The usual green accumulations on the glass are due to the presence 
of minute plants known as confer vse. They are generally considered 
to render the aquarium unsightly. This feeling, however, is not shared 
by those who are close observers and lovers of nature, for everywhere 
where even dampness is found this class of plants abound, making 
hosts of the larger plants and clinging to stones and sticks and even to 
the earth itself. Viewed under the microscope they are wonderfully 
beautiful. They are good oxygenators and furnish food for fishes and 
tadpoles and are really dense forests under the microscope in which 
myriads of animalculse harbor and propagate. If so desired, sufficient 
tadpoles and snails will keep these plants at a minimum, but if the front 
glass of the aquarium be kept free of them by the use of a small paddle 
or swab covered with rubber, felt, flannel, muslin, or chamois, they will 
be found to render it more beautiful by giving it the greenish tinge of 
nature. An excessive growth of them may also be checked by a modi- 
fication of the light by the use of screens, for which purpose the use of 
tissue paper is as good as anything. Some interesting experiments may 
be made upon the growth of plants by interposing tissue paper of dif- 
ferent colors and noting the effect of each after a few days. When the 
water itself becomes green and opaque from the presence of certain 
