FISH ENEMIES 149 



Hydra possess a poison which quickly stupefies their prey, and to 

 fish large enough to eat the hydra this poison doubtless has an unpleas- 

 ant taste. There is no fish known which will eat them. To get rid 

 of this pest, remove all fish, snails, etc., from the tank and place in 

 it one tablespoonful of household ammonia to five gallons of aquarium 

 water. Allow this to stand for two hours, change water and replace 

 fish. This treatment will not kill plants. 



LARGER ENEMIES OF FISHES 



It should not be understood that the foregoing are the only seri- 

 ous enemies of pet fishes. In the greenhouse, outdoor pool, or even 

 the library, misfortune is liable to descend in various guises. Chief 

 among these are the cat, rat, muskrat, snake, heron, kingfisher and 

 small boy. Fishes are also taken by the sandpiper, horned owl, cray- 

 fish, and blackbird. The latter specializes on picking out the eyes of 

 telescope fishes if the water is near enough to the edge of tank for 

 him to reach them. Frogs will eat fishes of nearly their own size. 

 Slow-moving fancy goldfishes are easy prey for them and inexperi- 

 enced fanciers have lost many of their best specimens through igno- 

 rance of this menace. 



The owner of the fish will have to use his personal ingenuity to 

 combat these enemies as occasion arises. The author must here con- 

 tent himself with pointing out the possible sources of trouble. 



Water Boatmen and Back Swdmmers (Corixidw and Notonectidcej 

 are found everywhere in still or slow-moving water. A considerable 

 injustice seems to have been done the Water Boatman by writers on 

 the aquarium, including the author, who have accused it of being an 

 active enemy of young fishes. Many goldfish breeders have 



Fig. 148. Water Boatman (Slightly enlarged) 



remarked that they never knev/ Boatmen to do any harm. The author 

 on this account conducted an exhaustive series of experiments, the 

 outcome of which is the vindication of the suspect, notwithstanding 

 eminent authorities to the contrary. Many hours and much eyesight 

 have been wasted picking small Boatmen out of collections of live 

 food. They are capable of inflicting a severe bite when handled, but 

 this is not sufficient reason to assume that they are predaceous. Large 

 hard-mouthed fishes like to eat them. 



