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The Museum Gazette 



friend living by or visiting the seaside may send us two or 

 three lively prawns ; or perhaps blennies or gobies from the 

 rock-pools on the shore. 



These must be introduced with caution and watched daily. 

 Any dead animal must be removed immediately, and directly 

 the anemones show signs of failing vitality, or the water 

 loses its brilliancy, we must remove some of the creatures 

 so as to restore the balance, and the life of the aquarium 

 must be revived by supplying oxygen. This may be done 

 by means of a glass or vulcanite syringe, and by agitating 

 the surface of the water with a stick. 



If necessary the depth of the water must be reduced for 

 a time. The water taken out should be placed in a shallow 

 vessel so that a large surface may be exposed to the atmo- 

 sphere. It will soon become bright, and may then be returned 

 to the aquarium. These expedients for supplying oxygen to 

 the water, although always useful, should not be necessary 

 in a well-balanced aquarium. 



The principle of compensation which renders it possible 

 to keep animals in a healthy state without change of water 

 requires a careful adjustment of animal and vegetable life 

 in such proportions as will ensure the healthy existence of 

 both. The carbonic acid gas given off by the animals is 

 taken up by the plants, which, under the influence of light, 

 decompose it, appropriating the carbon to their own use 

 and setting free the oxygen, which is taken up by the water 

 and rendered again available for respiration by the animals. 



It has already been pointed out that light is essential to 

 the well-being of an aquarium, but if too much light is 

 allowed to fall on it the result will be a rapid development 

 of confervoid vegetation which will soon render the water 

 green and in time obscure its contents. Periwinkles are 

 useful in getting rid of conferva when growing to excess on 

 stones, &c, but darkness is the only cure for the green 

 opacity of water loaded with minute vegetable organisms. 

 Temperature is another important element of success or 



