FISHFOOD 73 



Daphnia. Among the breeders of aquarium fishes, Daphnia holds 

 the supreme place of importance as a fish food. The fish will consume 

 great quantities of these crustaceans without suffering the usual effects of 

 being overfed. A certain degree of care must be exercised not to place 

 so many daphnia into the aquarium as to suffocate the fishes. Daphnia 

 breathe the free oxygen in water the same as do fish and therefore too 

 many will soon exhaust oxygen from water. The fish will die of suffoca- 

 tion sooner than the daphnia. Many beginners have lost fish in this way. 

 A good practice is to give the fish all they can eat in about a quarter of 

 an hour and still leave some few daphnia swimming about. 



A popular name for daphnia is "ditch fleas." This will give a hint 



Fig. SS Fig. 56 Fig. 57 Fig. 58 



Fig. 55. Daphnia (Greatly enlarged) 



Fig. 56 



Mosquito Larva (Greatly enlarged) 



Egg Raft and Individual Eggs (Greatly enlarged) 



Pupa Before Transforming to Mosquito (Greatly enlarged) 



Fig. 57. Cyclops (Greatly enlarged) 



Fig. 58. Cypris (Greatly enlarged) 



as to their appearance, as they are approximately the size and shape of a 

 flea, except that they have two rather long, branched swimming arms 

 which are always in motion and which give the animal a sort of hopping 

 motion through the water. Without this perpetual swimming the daphnia 

 would sink to the bottom, as they are heavier than water and have no 

 air bladder. A greatly magnified illustration is shown in Fig. 67. 



Daphnia (pronounced "daffney" in the vernacular) are known among 

 fish breeders as "insects," but they are really not such, being perfect 

 freshwater crustaceans as much as a crayfish. The shell, though soft, can- 

 not be digested. This helps the digestible portions to pass through the 

 intestines. This little creature is found in freshwater nearly all over the 

 world, principally in still pools where there are no fishes. For the 



