456 U. S. BUEEAU OF FISHERIES 



If collections of crustaceans and mosquito larv^ are made from 

 ponds for a food supply, the material must be carefully strained 

 through a fine sieve to obviate the possibility of water beetles, leeches, 

 and dragon-fly larvae gaining access to the fish and prej'ing upon 

 them. 



Only a few fish can be reared successfully in an ordinary fish 

 globe. An attempt to cany as many as 100 newly hatched goldfish 

 in a gallon of water would result in the gradual disappearance of all 

 the fry. Therefore, if only a small vessel is available for the pur- 

 pose it would be unwise to attempt to rear more than a dozen fry, 

 as the crowding together of an appreciably larger number would 

 undoubtedly end in complete failure. 



AQUARIUM CEMENT 



In the manufacture and repair of its aquaria the Bureau of 

 Fisheries has for many years successfully used a cement composed 

 of 5 parts of putty, 1 part red lead, and 1 part litharge. These in- 

 gredients are mixed to the proper consistency for glazing by the 

 use of boiled linseed oil and a few drops of dryer. A sufficient 

 amount of lampblack is added to change the color from red to slate. 

 After applying the cement allow it to dry thoroughly before put- 

 ting water in the aquarium. 



PONDS 



The first requisite for the rearing of goldfish in outside ponds is 

 a temperate climate, one that is not subject to protracted periods 

 of extreme heat or cold. If the work is to be conducted on an effi- 

 cient basis, a site should be selected in a part of the country having 

 natural conditions similar to those in Maryland, Virginia, New 

 Jersey, and Delaware, where settled weather may be dependecl upon 

 from about the middle of May to the end of September. 



The second factor for consideration is the water supply. This 

 should be constant and under control so far as possible at all times. 

 Too much stress can not be laid upon the importance of the latter 

 point. The pond site should be located where it will not be in the 

 path of destructive freshets, and in the construction of the ponds 

 every effort should be made to bring the supply under complete 

 control. Even under the best of arrangements a sudden downpour 

 of rain will often flood a pond system and cause the loss of fish. 



The most faA^orable source of water supply for a pond system is a 

 good spring, but in its absence successful results may be expected by 

 pi])ing water from a neighboring stream, provided it is of suitable 

 volume for the work and of good quality. The source should be at 

 a sufficient elevation to permit the water to flow by gravity from 

 one pond to the succeeding pond below. In this connection a slight 

 slope in the contour of the pond site is a great advantage, as it is 

 always desirable to provide for a fall of 5 to 6 inches between each 

 pond, thus making it possible to use the same water over and over 

 throughout the series. As a rule the last pond of a series is used for 

 the cultivation of daphnia and other varieties of live fish food. 



Some soils are not suited to pond construction, among them being 

 sand and gravel, through which the water seeps rapidly away. The 



