Fish

In Shepard's personal cabin, there is a large aquarium on the left side of the cabin which can be filled with fish. There are three types of fish available and the stores that sell them will restock after every purchase. Just as it is necessary with real fish, Shepard's piscine companions must be fed after every mission or assignment to ensure that they remain alive. Otherwise, Shepard must clean out the dead fish to allow the aquarium to be reused again. If Shepard had flirted with Kelly Chambers and invited her for dinner, the option to have her feed the fish will become available. Rearing fish does not appear to have any particular benefits except as an aesthetic purpose for Shepard's cabin.

Trivia

 * While in Citadel, Shepard overhears a krogan named Kargesh wondering whether if there are fishes in the Presidium.
 * Due to its unusual means of movement and tendency to swim "racetrack" circles, the Prejek Paddle Fish frequently clips right through the aquarium walls, swimming freely around in the air of Shepard's cabin, before drifting back into the aquarium. This usually happens right after feeding.
 * In Star Trek: The Next Generation, there is a fish tank in Captain Picard's ready room.