Covenant koi
From Halopedia, the Halo wiki
Covenant Koi are a species of fish similar to Earth koi and goldfish.
The Covenant apparently make similar use of them as humans do of their counterparts, namely that of a decorative pond fish. A school was kept in a garden in High Charity.
They can be found on the level Gravemind, in the central pond of the Valley of Tears B section.
