HATCHING TROUT 139 



air in hard water than in soft, ordinarily a 

 greater volume of the latter may be turned on 

 than of the former. But this cannot be taken as 

 a hard and fast rule. I know of a case where 

 three gallons of hard water per minute can be 

 flowed over the eggs and fry without harm to 

 either ; in a second case, also having hard water, 

 two gallons is about the limit. In a third hatch- 

 ery, where the water is soft, three gallons can 

 be used without disturbing the eggs, and in an- 

 other, of similar water, two gallons is ample. 

 It is important for a fish-culturist, no matter 

 how long he may have been in the business, to 

 study thoroughly all about the water he uses 

 in his plant, and also not to get it into his head 

 that because he has been successful in rearing 

 fish at one place, he must necessarily at once 

 have the same good fortune on another 

 property. 



Placing Trays. The trays on which the eggs 

 are placed should be submerged very close to 

 the bottom of the trough, or in such a position 

 as to provide the greatest amount of current 

 or aeration consistent with not moving the eggs. 

 As the trays are slightly narrower than the 



