104 



U, S. BUEEAU OF FISHEEIES. 



AQUARIUM CLEANER. 



The principle of the jet aerator may be successfully applied to a 

 device for cleaning aquaria, as shown in Figure 3. It is necessary 

 to use only a small amount of air in order to force waste material 

 from the bottom of the aquarium to a receptacle on the outside. 

 In fact, the air maj' be regulated so as to remove sand and gravel 

 from the bottom of the aquarium. It is obvious that the lower end 

 or intake should be provided with means for preventing the en- 

 trance of pebbles too large to pass through the outlet. 



Khi. o. - Aquarhim cleaner operated by air prest>ure in the .same manner as Figure 2. 



COST OF DISTRIBUTION. 



During the fiscal year 1923 the bureau honored 10,939 applica- 

 tions for fish, as compared with 10,376 in 1922. The following 

 table gives comparative figures showing the cost of distribution 

 for the fiscal years 1922 and 1923 : 



During the past 20 years the output of the bureau's hatcheries has 

 increased nearly 500 per cent, while the cost per thousand for trans- 

 porting fish has been reduced 50 per cent during this period. In 

 order to bring about this important reduction in distribution cost at 

 a time when the cost of transportation, material, and supplies was 



