The Goo Fish is one of Rita Repulsa's monsters who was sent to destroy Angel Grove Harbor.
He was chosen because Billy had a fear of fish ever since a fish bit his finger when he was young. Rita cast a spell on Billy that made him afraid of the monster. Fortunately, Billy overcame his fear and defeated the Goo Fish. Rita then made Goo Fish grow and he got destroyed by the Megazord.
He also made best one monster voice of Lord Zedd made by monster Goo Fish by best Rita's monsters create during episode "Something Fishy" in by Zyu2.