In this task, you're given a story (which contains five sentences only). Your task is to find all the characters which are available in the given story.
Q: Sentence1: Grady had a big aquarium. Sentence2: He filled it with tropical fish. Sentence3: He loved looking at the tank while he drifted off to sleep. Sentence4: He had big plans for adding more fish. Sentence5: The fish had become his favorite entertainment.
A:
Tropical fish, Grady