THE PUBLIC AQUARIUM 301 



other with their sharp teeth but will recover if isolated. Fishes with 

 fins damag:ed in capture or transportation can regenerate them. Sea 

 fishes frequently are blinded by fighting and, being useless for 

 exhibition, must be destroyed. 



Fungous growths may be checked or even cured by the use of salt, 

 permanganate of potash, peroxide of hydrogen, or mercurochrome. 

 Diseased specimens should be removed and the tank sterilized with a 

 strong solution of copper sulphate. A 2 per cent solution of mer- 

 curochrome is effective when painted on fungous spots of fishes. Two 

 applications will cure turtles suffering from closed eyes. 



"Water mold " (Saprolegnia), a fungus, is kept in check sometimes 

 by adding a small stream of sea water to the flowing fresh water. 

 Occasionally it is desirable to use permanganate of potash, 1 part to 

 1,000 of water, flooding the tank with this light solution for several 

 hours. Water mold sometimes is removed by brushing the spots with 

 kerosene. Sea fishes fortunately are free from fungus troubles. 



Costia, caused by a protozoan parasite, usually is controllable by 

 placing a large piece of rock salt in the tank, against which the fishes 

 are inclined to rub themselves. Strong solutions of lime water in the 

 tanks have been found useful in the treatment of Ichthyophthirius. 



Goldfishes suffering through failure of the slime organs to function 

 have been restored by dipping them in kerosene for a minute. Angel- 

 fishes that have become blinded by minute flukes have been treated 

 successfullj'^ with silvol. Gars covered with crustacean parasites 

 (Argulus) have been cleared of the pests by dipping in a solution 

 of mercurochrome. Some parasitic attacks have been combated suc- 

 cessfully with vinegar baths. 



It is not the intention to enter into details here as to the treatment 

 of ailing fishes in the large tanks of the public aquarium. With the 

 common and easily obtainable fishes the usual practice in this country 

 is to destroy those that are unsightly and replace them with fresh 

 specimens. This procedure may be convenient, but it is wasteful and 

 evades the difficulty altogether. The flow of water, its temperature, 

 filtration, and aeration, and the methods of feeding and tank clean- 

 ing may need attention. Overcrowding is a frequent cause of 

 trouble. The isolation of newly arrived fishes until their condition 

 can be ascertained is desirable. The fishes may be benefited by sand, 

 in which they often rub themselves. Caretakers may be unequal to 

 the diagnosis and treatment of disease, but with the help of a biologist 

 the difficulties often may be overcome. The numerous books written 

 by fish fanciers on the care of fishes kept in small aquaria usually con- 

 tain suggestions on treatment that are worth trying, but the handling 

 of large numbers of fishes in a public aquarium is more difficult. 



Aquarium managers are exchanging opinions on the results of their 

 experiments, and there is evidence that progress is being made. The 

 annual publications of the United States Bureau of Fisheries contain 

 many articles by biologists who have studied similar troubles in the 

 large fish hatcheries scattered over the countr}^ The aquarium 

 should be provided with these papers, most of which have been issued 

 separately and may be had upon application. The diagnosis of the 

 disease is less difficult, however, than its treatment. 



