AQUARIUM MANAGEMENT 13 



PLANTS 



We have now pretty well covered the important conditions regarding 

 aquarium water and taken several necessary side-excursions without 

 losing, it is hoped, the thread of the main ideas on oxygen and tempera- 

 ture changes. Now let us consider the plants, for they help in much the 

 same way as the water air-surface, but in a lesser degree. 



Plants Absorb the Waste Products of Animal Life and Give 

 Back Oxygen. The principle of exchange benefits between plant and 

 animal life in the aquarium was discovered in about the middle of the last 

 century, and as the idea took hold it gained a somewhat exaggerated im- 

 portance. The term "balanced aquarium" grew into use, meaning that 

 the plant and animal life balanced each other on a nearly equal exchange 

 of chemical elements. This mutually beneficial exchange undoubtedly 

 does take place. Plants in an aquarium without fish will virtually stand 

 still in their growth. On the introduction of fish a marked quickening 

 of their development can be noticed. The author is an intense admirer 

 of beautiful growing plants in the aquarium, and knows they have real 

 value of a practical nature. The fact is, though, we should not depend 

 upon them to compensate for overcrowding the aquarium with fishes. 

 This is for two reasons. First and most important, the plants only give 

 off oxygen under the influence of fairly strong direct or diffused sunlight. 

 This means that for more than half the twenty-four hours they are practi- 

 cally useless as oxygenators, to say nothing of their idleness on dull days 

 when barometric pressure is low and their services are most needed. The 

 second reason is that their oxygen-supplying activity is small compared 

 with that of the air-surface of the water. 



It must even be admitted that plants which are in a badly lighted 

 situation are likely to do more harm than good. 



Use plants, and plenty of them, provided there is good daylight. 

 They are beneficial and beautiful. No imitation of aquatic Nature is 

 complete without them. They are, however, frail friends, doing good 

 work when conditions favor them, but sleeping at critical times. 



The fish need plenty of oxygen all the time ; day, night and dull days. 

 Water-surface will not fail them, provided there is enough of it. 



There are many beautiful aquatics which may, under proper condi- 

 tions, be used in the aquarium. Those which can be readily obtained and 

 are of a useful character, as well as attractive in appearance, are few 

 in number. Of these, Sagittaria, in its different varieties, stands out in 

 importance above all the rest. The description of this and other plants 

 will be found in the following chapter on Aquarium Plants. 



Light. As above stated, aquatic plants in order to thrive and help 

 purify the water must have good light. When in the sun many of them 



