FRESH-WATER AQUARIA. 19 



FEESHWATER AQUARIA. 



BY R. M. LLOYD. 



Read before the Society, May ijth, 1881. 



As much pleasure and endless subjects for profitable study are 

 derivable from a well-managed fresh water aquarium, I offer a few 

 hints on the subject, based on a somewhat successful experience of 

 several years, and trust they may be of assistance to some of my fellow- 

 naturalists. 



The main point to be kept in mind, and on attention to which 

 success chiedy depends, is the imitation of nature — that is, the subjects 

 placed m an aquarium must, as far as possible, be surrounded by con- 

 ditions which form a near approach to those in which they naturally 

 grow and thrive. 



Excluding the inhabitants of the sea, all the many and varied kinds 

 of aquatic life may be roughly divided into those which live in ponds, 

 or comparatively slow running streams, and those which live in rapid 

 ones. This division will serve to indicate the reason why some animals 

 cannot be kept in an aquarium, for, generally speaking, it is only those 

 included in the latter group which do not thrive in an ordinary well- 

 managed tank. 



I have been many times asked the question : How often do you 

 change the water "? — and usually meet with expressions of astonish- 

 ment when I answer that it is unnecessary to do so at all. Yet, if 

 the inhabitants of the tank are in health this is quite correct, though it 

 is well, as we shall presently see, to have an occasional " clean out." 



There should be a proper proportion of animal and vegetable 

 life in an aquarium, or rather a preponderance of vegetable life ; 

 for, although such animals as are carnivorous, and at the same 

 time air-breathing, do not directly require it, yet, as they feed on 

 those who are or have been either vegetarians or water-breathers, 

 or both, indirectly they do ; as besides forming food-stuff, plants are 

 necessary to render the water capable of oxidising the blood of such 

 of its inhabitants as do not derive their supply of oxygen directly 

 from the air. 



Water absorbs oxygen from the atmosphere by the simple contact 

 of their surfaces, and if the superficial extent brought into contact is 

 very greatly increased, as by the formation of waves, the flowing of a 

 stream, and more especially by violent agitation, such as is caused by 

 the beating of waves on the shore, enough oxygea will be absorbed to 

 supply the animal inliabitants with all they require. As this cannot 

 take place in pools or other small pieces of water, the supply must, 

 consequently, be obtained in some other way. The action of the 

 chlorophyll or the green colouring matter of plants on the carbonic 

 acid gas contained in the water is the most constant method. It 



