Room for Ripley

The guppy in the pet store ripples through the water as he swims, so Carlos names him Ripley. Carlos wants to buy Ripley, though first he needs to set up a fish bowl at home with a little help from big sister Ana. He pours a cup of water into the bowl, but it isn't nearly enough. Then another cup, which makes a pint. But he needs more. How many pints make a quart? How many quarts in a half-gallon? In a gallon? It sure takes a lot of water to keep a little fish happy!