TREATMENT OF FISH-CULTURAL WATERS FOR REMOVAL OF ALG^. 885 



be held to coincide flatwise with the upper edge of the flame, meanwhile turning 

 slowly on its own axis, until it softens. The flame of a large kerosene lamp or 

 of an alcohol lamp will answer, but will not make as good a bend. 



Glass tubing may be neatly broken without cracking by slightly scarring 

 its circumference with a file at the desired point and then, by grasping the 

 tubing firmly with both hands, one on each side of the scar, pulling strongly 

 in a longitudinal direction, making simultaneously a slight stress at right angles. 

 A clean break will occur exactly at the scar. 



Nozzles, which are convenient as ends to the outer arm of the siphon, may 

 be made by drawing out in the flame several short pieces of glass tubing and 

 breaking off at some point along the constriction. They may be attached by 

 means of the usual rubber-tube connection. They are not necessary to deliver 

 the flow, and the outer arm may end merely by breaking off sharp; but they 

 give this advantage, that the length of the outer arm, or the size of its orifice, 

 or both, may be quickly changed with their aid, and thus the siphon flow may 

 be quickly and easily varied. For convenience a number of these nozzles may 

 be made, differing sulficiently in length or orifice to give different flows and 

 marked or labeled accordingly. By inserting a given nozzle a given flow may 

 be quickly obtained or a change quickly made. In making these changes 

 care must be taken not to change the length of the siphon arm above the point 

 of attachment of the nozzle if the labeled flow is desired. 



It is of course absolutely necessary that there be an intimate mixture 

 between the solution flowing from the siphon and the water flow which is being 

 treated ; otherwise a uniform dilution will not obtain. The sulphate will be too 

 strong in places and too weak in others, which may cause the loss of fish and 

 fail to kill the algae or accomplish the purpose desired. For this reason it is 

 well to deliver the siphon flow at the beginning of the conduit, so that mixing 

 may occur as the water flows. The agitation and mixing at the bulkheads of 

 ponds usually makes a uniform distribution of the sulphate. It will not do to 

 deliver the sulphate at a point where the water inflow to a pond enters quietly 

 with little fall, causing no mixing swirl. It may sometimes be necessary to 

 . provide special means for stirring to obtain a mixture. 



The stock solution of copper sulphate should not be kept in containers made 

 of ordinary metals. No metals should be allowed in any way to come into con- 

 tact with the solution. If the flow of sulphate solution to the water has to be 

 conveyed by troughs they should be of wood. Galvanized iron or tin is soon 

 eaten through, and usually can not by painting be sufficiently protected from 

 the action of the copper sulphate. Weak dilutions, however, such as those used 

 for testing susceptibility of trout, may be used in fish cans. The sulphate is 

 not strong enough to attack the metal notably. 



