THE CARE OF HOME AQUARIA 



17 



i ii ;ii i«i ' iBM i ii Jc gfWi - 



A BALANCED SALT WATER AQUARIUM. 



that in manufacturing their own food from simple substances 

 plants give off oxygen as a waste product. This process is ac- 

 complished by the green matter of the plant, a special kind of 

 protoplasm known as chlorophyll. In the submerged plants of 

 the aquarium the oxygen passes off directly by absorption into 

 the water. The fishes are thus supplied with oxygen given off by 

 the plants as waste substance. 



Having absorbed the oxygen into the blood by means of the 

 gills, the fishes combine it with the carbon of the food to obtain 

 energy, and, in the process of respiration, give off to the water 

 quantities of carbon dioxide, or carbonic acid gas, as a waste 



