Fish

Fish are a new collectible feature in Mass Effect 2 which has no impact on story or gameplay. 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 there are fish 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 or going through the ceiling and floor of the tank, before drifting back into the aquarium. This usually happens right after feeding.
 * The fish tank in the Captain's Cabin office area on the Normandy might be a reference to Star Trek: The Next Generation, in which there is a fish tank in Captain Picard's ready room aboard the Enterprise-D.
 * In Lair of the Shadow Broker, Liara has a fish tank in her apartment. It contains all of the fish that Shepard can acquire, in addition to jellyfish-like creatures.