300 U. S. BUREAU OF FISHEEIES 



miKl, but this material clouds the water and conceals the animals 

 entirely. However, there is no reason why sturgeons and other mud- 

 loving fishes should not be removed from the exhibition tanks 

 occasionally and placed in reserve tanks where they can have access 

 to mud for short periods. An emaciated fresh-water sturgeon that 

 had long refused food was sent to a small mud-bottomed lake in 

 Central Park a year ago, where it survived several months. 



At times there are sudden losses among trout that can be checked by 

 transferring all specimens to muddy water. The relationship of fishes 

 and other aquatic forms to their various environments can not be 

 disregarded, therefore, by those who w^ould succeed in keeping them 

 under such artificial conditions as obtain in the tanks and pools of 

 an aquarium. 



Fishes that are doing well should be shifted or otherwise disturbed 

 as little as possible. A " well-set " tank of fishes may thrive for 

 years if undisturbed. Mere additions may start trouble, Avith serious 

 results to the new arrivals. This is especially true among sea fishes. 

 We have seen a large queen triggerfish set upon by small fishes of its 

 kind and disabled in a few minutes. 



Additions to groups of tropical fishes are made more safely at 

 night in certain cases. Some fishes, in fact, feed by night and may 

 not get their share of the food that is thrown into a tank in daytime. 



Aquarium employees are liable to drift into routine methods of 

 feeding and tank cleaning that lead to unnecessary losses. The best 

 results can not be secured without careful attention to all operations 

 connected with the needs of things living in the aquarium. All 

 aquariums suffer losses through lack of study of individual cases. No 

 general method applies to all species. Mere rules can not take the 

 place of daily inspections by the manager. 



COMBINATIONS OF SPECIES 



The common aquarium practice of devoting a tank to each species 

 as far as practicable is not always best for the fishes. Many kinds are 

 gregarious and when grouped according to their capacity for dwelling 

 amicably with other species of similar size often do better than when 

 kept separately. The labeling of groups of species thus combined is 

 not so simple, and they are not identified so easily by the visitor, but 

 the exhibit is sure to be a livelier one, and the fishes find interest in 

 their more varied surroundings sufficient to prolong their lives 

 appreciably. Under such treatment they are not fed so easily. Active 

 feeders may thrive at the expense of those that feed slowly. Suitable 

 combinations can be arrived at only by experiment. There are many 

 kinds of familiar little fishes that flock together about the w^harves in 

 tropical waters and that can be kept together in the tanks of an 

 aquarium to better advantage than when separated by species. 



INJURY AND DISEASE 



Frequently there are fishes in an aquarium that have become 

 unsightly because of injuries, fungous growths, or ailments less sus- 

 ceptible of treatment. Fishes of the pike family may lacerate each 



