272 FISH CULTURE 



infest the tank, remove the fish and put in a 

 strong solution of permanganate of potassium 

 and leave it there for a day. The water may 

 then be drawn off and the tank washed out and 

 the fish given a bath in the washings. Fish 

 will stand permanganate of potassium much 

 better than is generally supposed. I had a 

 very convincing proof of this recently. More 

 than a handful of crystals of permanganate of 

 potassium got scattered by accident in a tank 

 containing 120 gallons of running water and 

 twenty-four long-eared sun-fish. This hap- 

 pened in the evening. The next morning, al- 

 though there had been a constant flow all night, 

 the water in the tank was bright red-purple. 

 Three fish were dead, and the remainder 

 showed very slight signs of life. All with any 

 life in them were placed in fresh running water 

 into which much air was forced. Twenty-four 

 hours later all except four had recovered, ap- 

 parently none the worse for the terrible experi- 

 ence. 



Signs of Illness. — ^In the majority of cases 

 where the water-temperature is right and the 

 water itself pure, if fish die suddenly it is the 



