THE ORNAMENTAL PLANTS — WINDOW-GARDENS 349 
making and keeping an aquarium: (1) The equilibrium between 
plant and animal life must be secured and maintained; (2) the 
aquarium must be open on top to the air or well ventilated; 
(3) the temperature should be kept between 40° and 50° for 
ordinary animals and plants (do not place in full sun in a hot 
window); (4) it is well to choose such animals for the aquarium 
as are adapted to life in still water; (5) the water must be kept 
fresh, either by the proper balance of plant and animal life or 
by changing the water frequently, or by both. 
The aquatic plants of the neighborhood may be kept in the 
aquarium, — such things as myriophyllums, charas, eel-grass, 
duckmeats or lemnas, cabomba or fish grass, arrow-leafs or sagit- 
taria, and the like; also the parrot’s feather, to be bought of 
florists (a species of myriophyllum). Of animals, there are 
fishes (particularly minnows), water insects, tadpoles, clams, 
snails. If the proper balance is maintained between plant and 
animal life, it will not be necessary to change the water so fre- 
quently. 
