[97] POND CULTURE. 5(53 



and spriugs or from ponds which are fed from these sourix'.s. To obtain 

 an even influx and outflow it is above everythino- else necessary that 

 all the ditches should constantly be kept in j^^ood repair, and from time 

 to time, especially after the flsheries, be cleaned .of mud and acjuatic 

 ]>lants. There is but little difiiculty in keeping up»a regular influx of 

 water, if th<' ponds are fed from brooks and rivers, and by weirs and 

 sluices this can easily be regulated. It is different in sky ponds, whose 

 supply of water depends on the accidental gathering of rain and snow 

 warer in fields and meadows. Here it will become necessary to keep 

 the ditches thnuigh which the water enters the pond in particularly 

 good rejjaii', to construct a large number of these ditches, and even, if 

 necessary, to bring the water from a distance. If any roads or dikes 

 arc in the Avay, the water slumld be carried underneath them through 

 ]»il)es or conduits, while it may be led round small elevations. As the 

 water in these ]>onds is a])t to be stagnant, and as a slight agitation 

 favors the absori)tion of oxygen from the air and thereby makes the 

 water healthier for the carp, the desired object is attained by letting 

 IIm; Avater flow into the pond over a weir, so that by its rushing motion 

 It keei)s up that constant nu)vement of the waters of the pond wiiich is 

 beneficial to the fish. To substitute weirs for grates may be recom- 

 mended in all those ponds which are fed by small streams or springs. 

 If ])onds are fed by brooks or rivers, the pressure of the water on enter- 

 ing the pond is generally stronger thanmay appear desirable for the fish, 

 and in this case, therefore, it will be preferable to let it flow in through 

 grates. For keeping the water at an even height the stand-jiipe may 

 be recommended, of which Ave have si)oken in a previous chapter. 



Clcuninfi out the mud. — To insure an even height of Avater, ami a reg- 

 ular supply and ontflow, no mud or aquatic plants in the ditches should 

 ofler any hindrance to the Avater in its flow. After the fisheries, there- 

 fore, all the ditches should be carefullj' cleaned. It is true that the 

 mud contains a great deal of nutritious matter, Avhile the aquatic plants 

 not only serA'c as food for fish but also sustain many insects which form 

 a favorite article of fish-food ; but it cannot be denied that too great 

 an accumulation of mud and too rank a groAvth of plants Avill contract 

 the water area very i)receptibly, and thus prove injurious to the fish. 

 To clean a pond of superfluous nnul and aquatic plants, it will be ne(;- 

 essary to drain it and dig ditches through the mud Avhich should all 

 open into a main ditch and carry the Avater towards the outflow. The 

 inud taken froui the tlitches is piled up in heai)S and allowed to dry in 

 Ihe sun and air. These mud piles arc not carted aAvay till Aviuter when 

 the ground is frozen, and should then remain exposed to the influence 

 of the atmosphere for at least a year before they can be used as a fer- 

 tilizer. This has also the advantage that the mud decreases at least 

 one-half in A'olume and Aveight, and offers much less dilficulty in cart- 

 ing it to the fields than if it had to be moved in its moist condition. 



The mud is removed from the different parts of the pond to its banks 



