Many people keep small fish _31_______ p

问题：

Many people keep small fish _31_______ pets. They keep them in a tank of water. The tank is made of glass. People can _32________ through it. They can see inside the tank and watch the fish.

The fish need room. They mustn’t be crowded. They need _33_______ to breathe.

__34_____ must be enough water for all fish. So the size of the tank is very important.

In the tank people put small plants __35________ are good for fish. They give oxygen to the water. Plants help in other ways, too. They can hide __36_______ the plants and sleep, lay eggs there.

The fish __37______ be kept in water all the time. Some can jump high. So the tank should be covered. This keeps the fish __38________ (jump) out.

The fish need food and should be fed every day. But __39____________ you give them too much food, it is very bad, for the extra food will fall to the bottom and make the water dirty. So the fish should get just enough food and finish __40___________ in ten minutes. Nothing should be left.