56 FISH CULTURE. 



■w^ater be filtered as shown above. The greater this 

 colleQtion of sediment, the more likely conferva is 

 to grow, as soon as the weather warms a little. The 

 slightest disturbance of the water raises this sedi- 

 ment in a fine cloud, and it then settles on the 

 eggs. This is, of .course, very objectionable ; for 

 although in moderately cool weather no great harm 

 may result, as I have said in warm weather con- 

 ferva will grow, and this will by no means improve 

 the condition of the eggs. 



Gravel also forms a home and a hide for vermin, 

 which, with every precaution, will at times find 

 its way in amongst the ova, and here, undetected 

 for some time, it will often work much mischief. 

 The ova cannot be so evenly spread upon gravel as 

 on the grilles, and much space is lost. A bad egg 

 cannot be detected nearly so soon on gravel as on 

 the grilles, and it often happens that a dead ova will 

 not be discovered until it has caused the death and 

 putrefaction of a dozen others, when the mischief is, 

 perhaps, discovered too late. Again, where a case of 

 this kind takes place, the gravel itself for some depth 

 becomes tainted, and ova, which may be placed in 

 the same spot, are very apt to take the contagion. 

 Jt is astonishing how gravel will become tainted, and 

 affect not only the ova but the fish ; and when this 



