MANAGEMENT OP THE AQTJABIITM. 47 



When the aquarium has been properly filled in the way 

 just described, it is a good plan, if patience will allow, to 

 postpone the introduction of any animals for at least ten 

 days or a fortnight — ^the longer the better. During this time 

 the plants ought to commence to grow and give otf "oxygen. 

 At first only a few occupants should be introduced — say, a 

 newt, three or four small fish, and a few snails — and if these 

 do well, one or two more may be added, and so on. When the 

 plants are fairly established, the aquarium will support much 

 more life than when they are only just beginning to grow. 

 If the fish swim near the surface of the water tails downwards 

 and mouths upwards, there are too many in the tank, and 

 unless some are speedily removed, many will die. There should 

 always be too few inmates in an aquarium rather than too 

 many; but if the tank is properly arranged, it is. really sur- 

 prising how much animal life it will support. For instance, 

 I have at the time of writing in a bell-glass aquarium, 19in. 

 in diameter, one gold-fish, one silver-fish, one carp, about a 

 dozen snails (Planorhis corneus), and at the least forty small 

 minnows {Cyprinus phoxinus). All these fish are seemingly 

 in perfect health, and have been so for about ten months. 

 The plants in this aquarium are Vallisneria spiralis and the 

 Cape Fragrant Water Lily {Aponogeton distachyon). 



The water of an aquarium that is properly balanced and cared 

 for, should never require changing, as a rule ; but circumstances 

 do occasionally arise in which it is necessary to empty the tank. 

 For instance, the water may have become corrupted by an un- 

 discovered dead body; the plants may need renewing, or the 

 rockwork re-arrangiag ; perhaps the aquarium has sprung a 

 leak, or it is necessary to remove it to some other position. 

 Any one of these circumstances would require the emptying 

 away of the water. This can easily be done by means of a piece 

 of india-rubber tubing, of about ^in. in diameter, used as a 

 siphon (Fig. 38.) Before the commencement of the withdrawal 

 of the water, as many of the fish and other inhabitants of the 

 aquarium as possible should be transferred elsewhere. How- 

 ever, it is not probable that all will be caught, for some 

 will hide themselves in the weeds or under the rockwork ; and to 



