THE AQUARIUM BULLETIN 



aquariums as well as the most interest- 

 ing I have ever seen, was a five-gallon 

 tank nicely planted, and with crystal 

 clear water containing twenty-five 

 Danio Rerio. The little fish darting 

 back and forth, displaying their colors 

 and graceful swimming, was indeed a 

 wonderful sight. 



The sex of the Danio is somewhat 

 difficult to distinguish out of the 

 breeding season. In the Spring, when 

 the roe is forming in the female it is 

 comparatively easy to determine. 

 The female at this period is always 

 much fuller in appearance than the 

 male and as the spawning period 

 approaches, this dift'erence becomes 

 still more marked, accompanied by 

 ceaseless racing up and down the 

 tank ; first the male chasing the female 

 and then the reverse. 



The Danio is not a difficult fish to 

 breed or raise if the proper precau- 

 tions are taken to protect the eggs, 

 and sufficient food supplied for the 

 fry. The adult fish have the dis- 

 couraging habit of devouring their 

 eggs as soon as spawned, and the 

 young as soon as they begin to swim 

 around. 



For spawning this fish it is well to 

 select a tank about sixteen inches long, 

 eight inches wide and six inches high. 

 Place three tiers of half-inch pebbles 

 on the bottom anchoring several 

 sprays of Cabomba or Myriophyllum 

 in the pebbles and adding about four 

 inches of old clear water taken from a 

 tank that has a heavy growth of algea. 

 The tank is placed in a position so 

 that it will receive all the direct sun- 

 light possible for at least two weeks ; 

 this will promote the growth of algea 

 and infusoria. 



The tank is then removed to a posi- 

 tion where it will receive onlv a rea- 



sonable amount of sun. A tempera- 

 ture of 70 degrees is then maintained. 

 Under these conditions I have known 

 them to spawn within two days, while 

 at other times, and under like condi- 

 tions, I have watched a pair that I 

 expected to spawn at once, for over 

 two months before I could see a sign 

 of an egg. 



When the eggs are discharged by 

 the female and fertilized by the male, 

 they do not adhere to the plants or the 

 sides of the tank, but at once sink 

 down between the pebbles and are thus 

 protected from the parent fish. If the 

 eggs cannot be seen, one may know 

 the spawning has occurred by the 

 appearance of the female. She will 

 have lost the fullness of body and will 

 again be difficult to distinguish from 

 the male. As soon as the eggs have 

 been dropped the pair should be 

 removed at once to another tank, 

 otherwise they will devour the young 

 as soon as they begin to hatch. 



At the above temperature the eggs 

 will hatch in about seventy-two hours. 

 The young fish first appear like 

 threads on the sides of the tank and 

 on the white pebbles. About twenty- 

 four hours after hatching the young 

 will be swimming freely with the same 

 characteristic movements of the 

 parents. If sufficient infusoria is 

 present they will grow very rapidly 

 and in ten days will begin to take the 

 smallest Daphnia and then grow by 

 leaps and bounds. 



Under ideal conditions — tempera- 

 ture and an abundance of live food — 

 the Danio will reach full size faster 

 than any other acjuarium fish. 



This fish can be especially recom- 

 mended to beginners and no collection 

 is complete without a few Danio 

 Rerio. 



^nSi,! 



