ZOOLOGICAL SOCIETY BULLETIN. 



849 



YOUNG CATFISH. 

 The local species of catfishes are hardy and interesting. They are excellent for the beginner 



a neater appearance after feeding time, but pre- 

 vents the escape of smaller particles to contam- 

 inate the water. Care in the matter of feeding 

 is of the utmost importance in preserving the 

 balance of the aquarium and in keeping the ani- 

 mals in good condition. It must be remembered 

 that the usual fault is that of overfeeding and 

 the conditions should be studied carefully. 



CLEANING THE AQUARIUM. 



It must be clearly borne in mind that clean- 

 liness is absolutely necessary to the welfare to 

 the inhabitants of the aquar- 

 i u m . Contamination can 

 arise only by bacterial decay 

 o f organic substances al- 

 lowed to remain in the 

 water. There are three gen- 

 eral sources of such organic 

 matter ; First, fecal matter 

 from the animals, relatively 

 unimportant because the de- 

 posits are small in amount 

 and regular in occurrence ; 

 second, decaying vegetable 

 matter from dead portions 

 of the plants, also relatively 

 unimportant since in the 

 well balanced aquarium there 

 is little tendency for the 

 death of the plant tissues, 

 and third, decay of excess 

 food matter, the usual source 

 of pollution. 



It is a common but very 

 mistaken notion that an ani- 

 m a 1 should have food a t 



hand at all times to keep it 

 in good condition. It is well 

 known that various forms of 

 domestic animals, as well as 

 the wild species confined in 

 zoological gardens, make the 

 best growth and keep in the 

 most satisfactory condition 

 when supplied only with what 

 food they will clean up at one 

 feeding. This applies with 

 equal force to the inhabitants 

 of the aquarium, but besides 

 there is a real and grave 

 danger of contamination in 

 supplying more food than 

 will be readily consumed. 



The first indication o f 

 serious pollution is a slight 

 clouding of the water caused 

 by the presence of countless 

 millions of bacteria. This may go on until the 

 water is of a milky color and the balance of the 

 aquarium is completely upset by the accumu- 

 lation of sulphur and ammonia compounds set 

 free in the water by bacterial decomposition. 

 How can the accumulation of dead matter be 

 prevented? The usual means is to introduce 

 some animal that will act as a scavenger to clean 

 up refuse matter. The forms generally made 

 use of are the tadpoles and fresh-water snails. 

 Either of these under ordinary circumstances 



SOFTSHELLED TURTLE. 

 Small specimens are well adapted to the aquarium. 



