In ten six-line stanzas, the poem relates a naturalistic animal fable. Three pet goldfish live in a bowl, but two are starved for nourishment by the greed of the third, which gobbles up their food and grows to enormous size as a result. One day, Johnny, the boy of the house, decides that the little fishes must be sick; he gives them medicine, in the form of one of his mother's pills. Naturally, the large greedy fish swallows this, and soon is dead. His compatriots grow "big and fat" themselves, once their competitor is no more.
In the 1898 collection, the poem is accompanied by a W. W. Denslow illustration.