Fish Maladies 333 



victim until the latter succumbs to their 

 ravages. Frequently fishes taken from 

 ponds and slow-running streams introduce 

 parasites into the aquarium. Of these, the 

 so-called fish lice can easily be discovered 

 with the naked eye or with an ordinary 

 magnifying glass. They appear as slightly 

 convex dots of a grayish green color and 

 can be removed with the thin sharp blade 

 of a knife. It is advisable to examine fishes 

 taken from local waters or bought from 

 local fish dealers, in order to discover such 

 sporadic parasites, as they will rapidly in- 

 crease in the narrow confines of the aqua- 

 rium. 



More dangerous than these large and 

 easily noticeable parasites are the minute 

 organisms which infest their host by the 

 thousands, and, not confined to one individ- 

 ual, destroy the whole contents of ponds and 

 aquariums by contagion. As soon as a fish 

 commences to rub its body against the bot- 

 tom of its tank or against any hard sub- 



