354 FISH HATCHERY MANAGEMENT 



Figure 110. Aerator-oxygen system designed and tested by FWS personnel at 

 Alchesay National Fish Hatchery, New Mexico, (l) Aerators mounted on top of 

 an aluminum tank. Note the electrical line for the 12-volt system. (2) Aerator 

 with a dual manifold extending through the false bottom of a tank. Water is 

 pulled through manifold (M) and discharged through aerator (A). (3) Aerator in 

 operation. Water is aerated and circulated and carbon dioxide is removed. (4) 

 The false bottom of the tank has been removed to show micropore tubing 

 (arrow) which disperses oxygen into the water. Note bubbling of oxygen through 

 the water. (Photos courtesy Alchesay National Fish Hatchery, FWS.) 



levels must remain within a tolerable range, and toxic levels of dissolved 

 ammonia and carbon dioxide must be suppressed. A partial solution to this 

 complex problem is aeration by sprays, baffles, screens, venturi units, 

 compressed gas liberation, agitators, or air blowers. Bottled gaseous or 

 liquid oxygen is liberated within tanks in a variety of ways, including per- 

 forated rubber tubing, carborundum stones, carbon rods, and micropore 

 tubing, or is injected directly into the recirculation system. 



Recent aeration innovations include a miniature water wheel that aerates 

 water during transport and the Fresh- flo^ aerator. The latter is commer- 

 cially available in ten sizes. The system depends upon centrifugal force 

 created by a high speed motor-driven impellor that pulls water into a sys- 

 tem of vanes, producing the turbulence needed to mix water with air, 

 while concurrently removing carbon dioxide. This aerator has been highly 

 satisfactory for transportation of warmwater fish and salmonids. 



