134 INTERRELATIONS OF PLANTS AND ANIMALS 



Observations. 1. As snails feed on plants, and small water 

 animals and tadpoles may feed on the decaying plant and 

 animal matter that is likely to collect, they may be used as 

 the animal life of a fresh-water aquarium. A small goldfish 

 might also be added. 



FIG. 38. A balanced aquarium. 



2. As such plants as algae and other water plants grow at 

 least as fast as they are devoured by the snails, it would seem 

 desirable that they be used as the plant life needed. 



Conclusions. 1. Fill in the following summary. Do the 

 two columns balance ? 



2. What is a ' balanced aquarium ' ? 



