72 FISH FARMING : 



something as near to it a,s possible; and it is comforting to 

 know that we can help Nature a lot in this connection. 



I think it is a pretty well established fact that trout will 

 thrive in a higher temperature of well aerated water than they 

 will in sluggish water. For instance, in a well aerated water 

 Faxio have been known to successfully battle with a tempera- 

 ture of TOdeg. and even more, while a sluggish water at GOdeg. 

 will sicken them and 70de. may prove fatal. Add at least 

 another lOdeg. in each case where rainbows are reared, and we 

 get a range of over 15deg. in favour of well aerated water, and 

 this often means the difference between success a.nd disaster. 

 This is why I have continually impressed upon my readers ihe 

 importance of having good falls where possible. It is also 

 advisable to " break up " the water supply as much as possible 

 before it enters into the rearing ponds or fenced-off portions of 

 a stream or river. In the case where the supply is taken 

 from a stream this can easily be done by placing. large stones 

 or boulders in the bed of the stream, and by the formation of a 

 series of small pools and succession of falls. Mr. Wilson 

 adopts a capital method of aerating water as it passes from 

 pond to pond. He places a sheet of perforated zinc parallel 

 with the surface of the water and through this the water falls 

 and is " broken up " after a very simple manner. This screen, 

 of which I give a photograph, is also a capital barrier against 

 fish mounting up from the pond below. The same gentleman 

 has devised a most ingenious method of aeration, where only a 

 very slight fall is obtainable, and this contrivance is shown in 

 Fig. 21. A is a dain that heads back the supply of water from 

 the stream, which passes into the pond through a six-inch 

 pipe, B B. An inch or inch-and-a-quarter pips, c, is fixed well 

 above the water level, and carried into the pipe B. The rush 

 of water through the pipe B automatically draws with it a large 

 and constant supply of air through the pipe c, and this is 

 forced into the volume of water? flowing into the six-inch pipe 

 at D and so into the pond E. Simple as this contrivance is, it 

 is most effective, and ensures a plentiful aeration consider- 

 ably more than occurs in the case of an ordinary fall of water. 



