n"rte Aquarium and Its Care 



JOHN LEE BENNINGTON 



PLANTS DOMINATE THIS SPLENDID AQUARIUM 



Photograph by George H. Seip 



The success of a self-sustaining aqua- 

 rium (a better term than "balanced") 

 depends upon the luxuriance of its 

 plants. It is many years, more than fifty, 

 since the discovery was made that plants 

 under the influence of light give off oxy- 

 gen. It is this process that makes the 

 aquarium possible. Like the land ani- 

 mals, fishes breathe. The impure blood, 

 heavily laden with the waste products of 

 the body, is pumped to the minute veins 

 of the gills, there coming in contact with 

 the oxygen in the water, the waste being 

 oxydized and cast off as carbin dioxide. 

 The plants then take hold of this com- 

 pound, break it up, retain the carbon 

 which they need for building new tissue, 

 and pass the oxygen back into the water ; 

 thus the oxygen practically acts as a car- 

 rier of carbon from the fishes to the 

 plants. Plants breathe, too, of course, 

 but the amount of oxygen they consume 

 is comparatively small in relation to the 

 quantity given off in tissue-building. 



From the foregoing it will be understood 

 that an aquarium will be self-sustaining 

 just as long as the supply of oxygen from 

 the plants is sufficient to meet the needs 

 of the animal inmates. The old term 

 "balanced aquarium" was wrong, in that 

 it inferred that a state of equilibrium ex- 

 isted between the plants and fishes ; if 

 such was really the case the balance 

 would be continually hovering between 

 success and failure. This close correla- 

 tion of the needs of the two forms of life 

 cannot pertain. The plants must domi- 

 nate in the tank, and must at all times 

 be liberating more oxygen than the fishes 

 will consume. If more than the water is 

 able to retain, and the power varies with 

 the temperature, it will be passed off into 

 the atmosphere. Not so, however, the 

 carbon dioxide. This is a heavier gas 

 than oxygen, and more easily retained by 

 the water. 



As has already been explained, the real 

 foundation on which the little water 



