In stocking an aquarium it is most essential that the number of fish introduced be no greater than 

 the available supply of oxygen will easily maintain. Small fish are preferable to large ones, because 

 they require less attention and more can be accommodated; and those 2 to 5 inches long are the most 

 satisfactory. For fish 3 inches long or less, there should be two-thirds of a gallon or one gallon of 

 water apiece, while for specimens 4 to 5 inches long at least two gallons of water apiece should be 

 provided, in a balanced aquarium. 



To make an aquarium balanced or self-sustaining, it is necessary to introduce plants that are 

 adapted to such an environment. There are many kinds of non-flowing plants that combine utility with 

 l>eauty, and in almost every community water plants suitable for introduction into aquaria may be 

 found in ponds, lakes, and streams. Among the most desirable are milfoil (Myriophyllitin}, hornworl 

 (Ceratophylhtin), eel-grass (Vallisneria'), fanwort (Caboniba], pond weed (Potamogeton), swamp 

 loosestrife (Ludungia) , and water weed (Anacharis). 



Two or three kinds of the foregoing are sufficient for one aquarium, at one time, and the species 

 may be varied at frequent intervals if desirable. A good combination is a floating plant with a rooted 

 one. In a large aquarium some of the flowering plants like the water hyacinth (Piaropiis) or tile- 

 arrowhead (Sagittaria) may be inserted in limited numbers. Various filamentous algae are likely to 

 be introduced incidentally with the other plants, and unicellular algse are certain to occur and at times 

 may multiply to such an extent as to make the water green and turbid, thus obscuring the fish. Alga: 

 frequently coat the glass sides of aquaria, and may necessitate the cleaning, particularly of the front, 

 in order to permit a proper view of the interior. A superabundant growth of plants will require 

 removal of the surplus or a diminution in the amount of light. 



Bottoms of house aquaria may be covered to the depth of I 1 /, to 2 inches with gravel or clean 



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