Keeping fish as pets is a popular hobby. Fish take up little room, are inexpensive to feed, and provide an interesting and color1ful display in any room.        A tank, or an aquarium  , must be chosen carefully. Many new aquarium owners buy too many fish for their tanks. Fish cannot be crowded. Two fish can live comfortably in each gallon of water, only ten fish can live in a five-gallon tank. Can you see why a goldfish would not live long in a tiny , round bowl?        If too many fish are kept together, they will not have enough oxygen   or room to swim about freely. They will have more diseases. Also, some kinds of fish cannot be kept together. They will fight and may even kill one another. As your interest in fish grows, the number of fish you have may grow, too. Then you may want to  _ in another tank.        If you start with a ten-gallon aquarium, what kind of fish would be best? The two major groups of tropical   fish are those that lay eggs and those that give birth to live young. If you want to raise young fish, guppies   would be the best choice because they can produce many babies in a short time.         You can buy fish and aquariums in most pet stores. Ask the owner to help you choose the right fish. You can also find many books about tropical fish in the library. What can we know from the passage?
Very few people are interested in keeping fish. The size of your tank decides how many fish you can buy. Guppies are a kind of fish that are good at laying eggs. You can raise different kinds of fish together.