PLANTS AND OTHER CONSmERATIONS 6l 



moval of gaseous waste such as carbon dioxide and 

 ammonia is necessary. In nature both replenishment 

 of oxygen and removal of gaseous waste is by ex- 

 change at the water's surface and by photosynthesis. 

 The former is greatly aided by surface agitation by 

 wind. In the aquarium environment fishes are usually 

 more crowded and surface exchange and photo- 

 synthesis do not always proceed at a normal rate. It is 

 thus customary to aerate tanks by compressed air, 

 mechanical agitation, or by circulation. Air pumps or 

 compressors vary greatly in their capacities and de- 

 sign. It has been pointed out earher that air pumps 

 for aquaria aeration should be of a high volume, low 

 pressure type. Further, the need is for a continuous 

 flow of air. A number of small pumps on the market 

 are made specifically for aerating aquaria. Some of 

 these units are a diaphram type while others are 

 piston type. They can adequately aerate several tanks, 

 however, for numerous tanks and for larger tanks it is 

 advisable to obtain a rotary pump of approximately 

 one-quarter horsepower. 



Closely associated with the use of compressed air 

 for aeration is the use of air dispersement devices. 

 Air stones are the conventional air-dispersing device, 

 but the author has made excellent dispersers from 

 thick-wall, one-quarter inch diameter, polyethylene 

 tubing perforated with a fine needle. 



For tanks in the 300-gallon class and up, aeration 

 can more eflFectively be accomplished by the use of 

 agitators (Figure 6). Suitable agitators are available 

 from companies dealing in bait minnow supplies. 



Running water may be sprayed or splashed to 

 aerate it. If circulating or flushing is being done, a 



