The Koi Carp is a fish caught in the Grove using the Fishing Rod from Derris. It is catchable in Spring, Summer, and Winter from 11:00 - 17:00 and again from 20:00 - 06:00 in all types of weather. Worm Bait is required in order to catch.
It can be found in the 12th spot of the Pond Fish section of the Collection Book.