20 METHOD OF DESTROYING ALG^ IN WATER SUPPLIES. 



Efect of various concent ratio) is of roppcr sulphate upon different Joruis of aUjie — C'ont'd. 



G-ROUP S— Continued. 

 ANAB.ENA CIRCINALIS Raben. 



ANAB^NA FLOS-AQU.E Breb. 



UROGLENA AMERICANA Calk. 



The foregoing tables clearly demonstrate the effectiveness of copper 

 sulphate as an agent for the destruction of algne, and as the cost 

 for an amount of this salt necessary to make the strongest solution 

 required will not exceed from 50 to 60 cents per million gallons, but 

 one condition remains to be satisfied — that it shall be absolutely harm- 

 less to man, domestic animals, and fish under the conditions used. 



In general, animal life is less susceptible to injury by copper than is 

 plant life, though most of the higher plants, some of the fungi, and, 

 as the preceding tables show, certain alga? will live in concentrations 

 of copper sulphate that would be fatal in a few hours to fish and frogs. 

 The critical concentration for game fish is higher than that for such 

 fish as carp and catfish. Black bass in good condition have endured 

 concentrations of 1 to 50,000 for many weeks with no apparent discom- 

 fort, while 1 to 100,000 was sufficient to kill German and mirror carp 

 in a few hours, and 1 to 500,000 killed the most susceptible in a few 

 days. Mud catfish are affected at practically the same concentration; 

 goldfish at slightly greater, while yellow perch are perhaps less sus- 

 ceptible than goldfish. This agrees with the results of Perry and 

 Adams,« who state that minnows and goldfish live indefinitely in a 1 

 to 200,000 solution. 



« Perry & Adams, 4th Kept. River Point. Conn., 2: .S77-391. 



