Dogs are stinky and stupid. Cats are unfortunately independent and shed a lot. Birds are noisy and shit just about anywhere. No one can take you seriously if you have a pet hamster. What's a character to do? Get an aquarium. Fish are essentially moving props[[hottip:*:Just like actors.]]. Occasionally they're very pretty moving props. An aquarium adds a great deal of vitality and interest to a scene without the annoyance you get from even the best trained dog or cat. Fish also make pretty darn good pets! They're cute/pretty, they don't shed, and depending on the species they can be as close to cuddlesome as you can get when any personal interaction would risk suffocation for one of you. Pets allow a character to have a bit more personality; caring for another living thing, even a goldfish, let's a character connect with another creature. It sometimes shows a character is rich and sophisticated; a villain might have a huge aquarium full of expensive and exotic fish. If a villain doesn't have a Right-Hand Cat, his second choice of pet is likely to be a tank with vicious or poisonous fish, like sharks or piranhas. A tank full of dangerous marine creatures used as a Death Trap is a Shark Pool in which the Hero is Fed to the Beast. Sometimes the aquarium is just intended to evoke an alien environment; most of us don't have floor-to-ceiling aquaria full of deep-sea creatures in our bedrooms. Expect most any cartoon cat to get mixed up with the denizen of a fishbowl or aquarium at least once in his career.
- Cos, Bish's erstwhile best friend in Sneakers keeps a large tank full of tropical fish. No interactions, but combine it with his futuristic tech, his minimalist office, and his armed thugs, and you've got yourself a Bond Villain.
- The villain of National Lampoon's Loaded Weapon (played by Tim Curry) keeps a tank full of piranha to show how Bad Ass he is. Then he proves it by sticking his head in the tank and grabbing one with his teeth.
- Ken in A Fish Called Wanda
- Became a source of conflict in Jungle 2 Jungle.
- James Bond ends up near these a lot.
- Total Recall. Big Bad Vilos Cohaagen has an aquarium filled with fish. At one point it's tipped over and the fish are shown gasping for air, a Foreshadowing of a scene at the end where several characters end up exposed on the Martian surface.
- Deuce Bigalow features a large aquarium, mostly present for very serious drama.
- In Mission: Impossible, Ethan ends up escaping from the CIA by blowing up an aquarium using bubblegum.
- In Star Trek IV, Captain Kirk wants an aquarium. And he puts a whale in it.
- Free Willy may well be the apotheosis of this trope.
- The Incredible Mr. Limpet. As a sign of his infatuation with fish, the title character has an aquarium in his home.
- The dentist in Finding Nemo.
- Disney's Pinocchio. Geppetto has a pet goldfish named Cleo that he keeps in a small glass bowl.
- Hildegarde Withers, the schoolteacher/amateur sleuth in a series written by Stuart Palmer, collects tropical fish.
- Willow of Buffy the Vampire Slayer has a small aquarium. Mostly so the Big Bad of the second season can slaughter them to evoke maximum terror. He was right by her bed. Good thing she didn't get that puppy.
- On ER, Luka had a large aquarium. Abby broke it. After she broke up with him. She tried to replace it without him knowing. It didn't end well.
- Mulder on The X-Files kept fish in tank in his apartment. Feeding them was a convenient excuse for whenever Scully was discovered by M.I.B's looking for classified documents or evidence or whatever in Mulder's apartment.
- NYPD Blue: Sipowitz has tropical fish at home and at the squadroom. At one point another character (don't remember who just now, not one of the regulars) accidentally killed his squadroom fish while he was away.
- Mr. Rogers had fish in a tank which he fed Once an Episode.
- Captain Picard, of Star Trek: The Next Generation, keeps an aquarium in his office.
- Starting in Mass Effect 2, Commander Shepard can start collecting Space Fish. They might die if you don't feed them. This continues in the third game.
- Penguin has an aquarium in Batman: Arkham City. It's very understated, with only one fish.
- The Simpsons have an aquarium, but only when needed to further the plot.
- In one episode, Troy McClure's bedroom is shown to have an enormous aquarium as its centrepiece, and it's rumoured among Springfielders that he uses the fish for sexual purposes.
- Cornelius Fillmore kept a carnival-prize goldfish in a bowl on his desk. Next to his partner Ingrid, it was his best friend in the world. He was saddened when it died.
Hello, Unknown Troper. You'll need to get known to lend a hand here.