*20 FRESH-WATfiR AQUARIA. 



decomposes it into its two elements, carbon and oxygen ; appropriates 

 the former to its own use, and liberates the latter for that of animals. 



Hence it will be seen that, although some amimals may be kept in 

 an aquarium without plants living with them, it can only be by the 

 aid of extraneous assistance ; food must be placed within their 

 I'each ; and the water must be aerated by agitation or some other 

 mechanical means. 



The first requireiiieut is a vessel to contain the water. This may be 

 made of almost any material, but the sides should either be vertical 

 or inclined from the bottom outwards. '• Fish globes," with the water- 

 line above the greatest horizontal diameter, are to be shunned as the 

 very worst form. A slate tank with plate glass front is by some con- 

 sidered the best vessel for an aquarium. I am, however, iuclmed to 

 think that the use of rough plate glass for the sides and back would 

 be au advantage, but an ordinary glass pan of about sixteen inches 

 diameter and six inches deep will do exceedingly well ; such vessels 

 are sold under the name of " pastry pans," I believe, and cost about 

 half-a-crown each. Ordinary propagating glasses inverted and held in 

 position by a base turned out of a block of wood make very good tanks ; 

 small hand glasses, of about four inches diameter, placed on the top 

 of hyacinth vases are also very useful, and are not unornamental. Pickle 

 bottles, earthenware pans, and other such like ordinary vessels may 

 frequently be used as auxiliaries with advantage. 



The best water to use is generally that in which the animals have 

 been found thriving, but such as is ordinarily supplied by water-works 

 is admirable for aquarium purposes, being m many cases filtered stream 

 water. Rain water will do for many things, but pump water is to be 

 altogether avoided. 



The bottom of the tank should be covered with about an inch of 

 grit and fine gravel, on which it is well to place some pieces of i-ock or 

 rough stone. It is better to avoid limestone in any form, and use slaty 

 or siliceous stones only. Resting and hiding places are thus formed 

 for the animals, and plants are better preserved from being uprooted. 



I consider the American weed t Anacharis Alsinastrum) the best for 

 aquaria, as none thrives so well or affords better food. It, moreover, 

 furnishes a good example under the microscope of the circulation of 

 cell contents, and the quantity of oxygen given off by it when freely 

 exposed to the sun's rays is very great, the bubbles of gas ascending 

 from it in continuous streams. The Anacharis also requires no care in 

 removing and planting; any scraps thrown into the tank will soon send 

 down rootlets from the joints and anchor themselves among the 

 gravel ; and even if any of the larger burrowing molluscs are kept in the 

 tank, the plants, though being constantly uprooted, will still con- 

 tinue to grow. Microscopic treasures are frequently to be met with 

 on it in abundance, but perhaps not so many in number as on the 

 Water Milfoil, (MijrioplujUum,) which is another very good plant for an 

 aquarium. Chara and Nitella are also good. Vallisnena spiralis is very 

 pretty and interesting, but it requires a rather deep tank, and Us roots 



