FISHES DIAGKAM 5. 97 



aquarium, nor too large ones, nor carnivorous animals, which 

 would eat the others. People often forget that the animals in an 

 aquarium must be fed like a bird in a cage, or a dog which is 

 kept chained up. We must try to find out suitable food for the 

 animals that we rear ; no doubt some will find what they like in 

 the water ; but it will not do to depend on that. If there are 

 not many animals, and if there are some plants with them, and 

 too much food is not thrown in so as to spoil the water, it will 

 preserve its clearness for a long time, and it is unnecessary to 

 change it. At the end of some time, we shall observe some small 

 insects and molluscs which we did not know to be there. The 

 surface of the glass will be covered with slime, but it can be 

 cleaned without disturbing anything, with a piece of rag tied on 

 a stick. A sea-water aquarium can be easily managed when it 

 has once been stocked. It is then enough to make a mark to 

 show the level of the water. When it has sunk by evaporation 

 below the mark, we must add fresh water as far as the mark, 

 and we can in this manner keep various marine animals alive 

 for a very long time. 



Carp. The carps form a large family which also includes the 

 barbels, tench, whitebait, and goldfish ; the scales of the carps are 

 large and rounded, and these fish all feed on plants, and only 

 rarely touch animal food. 



The carp inhabits our rivers, but it also likes ponds, where it 

 sometimes grows to a very large size. It has been proved to 

 live a very long time, at least 150 years. 



The whitebait is sought after for the sake of a kind of silvery 

 dust under its scales, of which false pearls are made. It is also 

 considered a great delicacy, for which Greenwich is especially 

 famous. 



The goldfish was brought from China about a century ago, and 

 has multiplied so much in our country that it is now very com- 

 mon in a semi-doniesticated state. 



Salmon. The salmon family only includes the salmon and 

 trout. Young salmon have their skin marked with small 



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