[113] POND CULTURE. -,70) 



increase to at least Impounds apiece, making an increase of three-quarters 

 pound per fish ; the total increase for the 2.000 would therefore be 1 500 

 pounds, which, counting the pound at 50 pfennige [12^ cents], would rep- 

 resent the sum of 750 marks [$178.50]. It should be remend)erod that 

 if an additional number of fish, like the one referred to above, is placed 

 in a pond, regard should be had not only to a proper supply of food, 

 but also to an ample area of water. We would require, for a period of 

 one hiuidred and eighty days — April to September, inclusive — for the 

 2,000 original and the 2,000 additional fish (all in one pond), which 

 supplies food for only 2,000, the following quantity of food : ISO x 4 = 720 

 pounds albumen and 3C0 pounds of hydrates of carbon. Add to this 

 oue-lia]f more, in consequence of the increase of the rations correspond- 

 ing to the growth of the fish, and the total quantity of albumen to be 

 supplied would be 1,080 pounds. To supply this we would need, say, of 

 meat dried and ground fine, 15.G hundred-weights, at 15 marks [$3.75], 

 making the total outlay 234 marks [$58.50], Subtracting tl)is amount 

 from the gross income, given above, we woidd get a net i)rofit of 

 510 marks [$120J. 



It appears from these figures that even a comparatively expensive 

 food will pay in the end, which result, in part at least, is brought 

 about by the fact that this food possesses, at any rate, approximately, 

 the correct proportion of nutritive substances. In order to i)rovide the 

 desired quantity of hydrates of carbon it will of course be necessary to 

 mix with the ground meal some other food containing less nitrogen ; 

 this will rather diminish than increase the price of the food. The addi- 

 tion of some article of food containing less nitrogen will be all the more 

 necessary — if the ground meat, as in the example given above, is to 

 be used almost exclusively — because otherwise the fish would not get 

 the needed quantity of alkali, of which ground meat contains but little. 

 I As regards supplying the necessary quantity of hydrates of carbon, it 

 may not always be required to add anything to the ground meat, as the 

 proportion of hydrates of carbon may vary from 1 to from 0.4 to 0.5. 

 'For this very reason I have selected ground meat as an illustration, be- 

 ^ cause the calculation will be simplified; also because it is one of the 

 ■most expensive articles of food, but can be easily furnished at any time 

 and in any desired quantity, which, of course, is not the case with ar- 

 Iticles like blood and refuse from slaughter-houses, excellent as they 

 may otherwise be. It also applies here what Professor Wolff says in 

 ,his Rationelle FUtterung der landtcirthschaftUchen Nutzthiere, 1814 

 ^'(Rational method of feeding domestic animals), p. 191, "that the rules 

 ;iaid down for feeding should be followed only in their general outline, 

 land that it is not necessary to have everything agree down to the least 

 •fraction." 



I Next to ground meat, fish guano may be recommended for feeding 

 tearp, because it possesses excellent nutritive qualities, and can easily 

 be obtained. In order to obtain the quantity of albumen in animal 



