46 MAINTAINING FISHES 



with the production of wart-like growth on the fins. 

 Probably more important among captive fishes, espe- 

 cially guppies, is a dropsal condition that may be of 

 viral origin. 



There are presently no chemical treatments for viral 

 diseases of fishes. The only approach to the problem 

 at present is to discard the fishes and obtain new 

 stock or utiHze a different species if feasible (see Wat- 

 son 1954). 



Fungal Diseases 



There is considerable conflict of opinion con- 

 cerning the importance of fungi as fish pathogens. It is 

 generally agreed that water molds of the genus 

 Saprolegnia are the principal forms involved. It is also 

 generally accepted that Saprolegnia is most important 

 in the infection of fishes that are damaged, diseased, 

 or suffering from malnutrition. There appears to be a 

 relationship between temperature and fungal infec- 

 tions. Lower temperatures favor molds. Thus, when a 

 mold problem becomes evident, an increase in water 

 temperature may be a solution. Molds are also en- 

 couraged by accumulation of excess food in tanks. 

 Molds constitute a special problem in the case of fish 

 eggs. Successful hatching in some cases may require 

 an increase in temperature or treatment of the eggs 

 with a fungicide. 



Various other maladies are frequently diagnosed 

 as fungal. White discoloration on fishes is not neces- 

 sarily evidence of a fungal infection. Many infections 

 as well as certain chemical damage can cause white 

 discoloration. The presence of the cotton-like growth 

 of mycelia, however, indicates that Saprolegnia is in- 

 volved. 



