THE FRESHWATER AQUARIUM AND ITS MAINTENANCE 



be put in the water, least of all after smoking; the aquarium should be 

 covered when sweeping, and the room frequently aired or ventilated in mild 

 weather. The dust may be removed from the surface of the water with 

 a piece of clean blotting paper, but it soon settles to the bottom and 

 serves as food for the scavengers and forms a part of the humus or residuum 

 on the sand or pebbles. When the humus layer becomes thick, it may 

 be injurious, and should be removed with the dipping-tube, the water 

 siphoned, or the aquarium cleaned. In an experimental aquarium con- 

 taining twenty gallons of water, this humus had formed fully half an inch 

 thick, the water not having been changed for eighteen months, yet the 

 fishes were perfectly healthy and contented. It is best to remove it, how- 

 ever, as it is the culture medium of parasites and fungi, and it is not 

 advisable to leave it so long in the aquarium. 



A piece of charcoal floating on the water or weighted and hidden 

 among the plants serves as a deodorizer and mild antiseptic, and can be 

 introduced to advantage. 



Alg^e. Algae on the glass may be removed with a brush or a piece 

 of felt on a stick or rod. It is advisable, however, to leave it on the sides 

 which do not obstruct the view, as it aids in screening the fishes from ex- 

 cessive light and in keeping the water in good condition. A fish showing 

 signs of illness, will often speedily recover when removed to a tank filled 

 with green water, as it contains not only desirable food, but also beneficial 

 medicinal properties. A very little permanganate of potassium will check 

 the growth of Algae, if this is found to be objectionable. 



Destruction of Plants. Even when sufficiently fed, the fishes 

 will sometimes tear and destroy some of the aquatic plants, feeding on the 

 younger shoots; but this is often done in sheer mischief and wantonness 

 and the remedy is to introduce more of those plants which are unmolested. 

 It may also be noticed that the fishes take the sand and smaller pebbles 

 into their mouths; they do this to feed on the tiny water plants growing 

 upon them, and it is not always an indication of insufficient feeding. 



In conclusion it would be well to recapitulate the principles leading 

 to success with the properly conditioned aquarium, any mistakes of which 

 will surely lead to failure: — absolute cleanliness with everything pertaining 

 to the aquarium; proper and abundant light; a vigorous growth of desir- 

 able aquatic plants; absence of decaying vegetation, a proper balance of 

 plant and animal life, with preferably a. preponderance of the former, ab- 

 sence of parasites and diseases^ sufficient scavengers; and care in feeding 

 the proper food. 



34 



