932 BULLETIN OF THE BUREAU OF FISHERIES. 



more difficult to cure, and was fatal in more cases than at any time in the his- 

 tory of the aquarium. Salt-water treatment did not cure as before, and the 

 use of hydrogen dioxide was commenced. If a fish has only two or three diseased 

 spots, it may be taken out of the tank with a net and the dioxide applied with 

 a sponge. When the fungus is distributed over a considerable portion of the 

 body, the fish is immersed in a solution of one part hydrogen dioxide to three or 

 four parts of water. The length of time fishes will endure the treatment varies 

 much with different species. It is necessary to watch them closely or some 

 will be injured or killed. 



Fungus has been killed on hundreds of fishes, of many species, in the New 

 York Aquarium, by the application of hydrogen dioxide, and the fishes have 

 been kept on exhibition for weeks, when they would have died in a few days 

 without the treatment. Treatment for fungus should commence as soon as 

 it appears; if not, it soon eats into the body and weakens the fish, making the 

 cure more doubtful. 



After treatment it is most necessary to take precautions against a recurrence 

 of the fungus. In my experience, in many cases it is not difficult to kill fungus 

 on fishes, but when this is done the affected place is left a sore, and the fish is 

 more or less weakened by the disease and treatment. Therefore, when put 

 back into the tank in the same water from which the disease was contracted, 

 the fungus soon appears on the places formerly affected. Each recurrence 

 reduces the strength of the fish and in many cases death occurs in time. I beUeve 

 that if after treatment the fish could be put into new water practically free from 

 fungus the sores would heal and the disease would not reappear. A human being 

 contracts pneumonia and recovers, but is not exempt from contracting the 

 disease again; in fact, under the same conditions, he may be more liable to a 

 second attack. 



In March, 1908, when fungus disease was so prevalent in the aquarium, there 

 were two tanks of fishes, one of rock bass (Ambloplites rupestris) and the other 

 spotted or channel catfish {Ictahirus punctaius) , both of which species were 

 attacked. Salt water was used, but without any beneficial effect. Hydrogen 

 dioxide solution was used until the fishes were entirely cured. At the present 

 time, September 10, 1908, every specimen of both species is in fine condition. 



Fishes in house aquariums can be treated for fungus by taking the diseased 

 specimen out of the aquarium and immersing it in prepared salt water, or in a 

 solution of hydrogen dioxide. A small quantity of either preparation will be 

 sufficient. If kept for some time, the dioxide will lose strength and become 

 less effective. 



