52 DOMESTICATED TROUT. 



um-sized tanks than to have one excessively large 

 one. 



I should call the first of the two just mentioned a 

 medium-sized one, and the second a large one, as 

 large, perhaps, as should be made. 



The outlet of the filtering tank should be at least 

 six inches lower than the top of the tank, to guard 

 against the water escaping over the top when the 

 screens clog up. There should be two holes at least 

 an inch in diameter in the bottom of the tank, to let 

 the water off when necessary, and they should be 

 plugged with very long stoppers, which will come 

 nearly to the surface, so that they can be withdrawn 

 without the arm being much immersed in the water. 



The filters themselves may be made of any kind 

 of strong, coarse flannel. White has the advantage of 

 showing dirt best, and red, Seth Green says, will last the 

 longest ; otherwise, one color will do as well as another. 



These filters must be watched, and, no matter how 

 often they require it, they must be taken out and 

 cleaned as soon as they are dirty; but in doing this the 

 rear one should be moved as little as possible. If 

 you clean while wet, wash them under water, either 

 with a brush, or a long-handled stick smoothed at the 

 end j the brush is the quickest method, the stick 

 wears them out less. If you have a chance to dry 

 them, the deposit on them can be easily brushed off 

 with a dry brush. It may be necessary to clean the fil- 

 ters every day. If it is, do not neglect it. The tank is 

 placed, of course, at the outlet of the spring aqueduct, 

 which is usually at the head of the hatching-room, and 



