Exploding Fishtanks

In action movies, it has become almost mandatory that if an aquarium is shown at any point, the aquarium will inevitably be destroyed, spilling the water and all the poor fish it contains out onto the floor. Sometimes this is the result of collateral damage, the fish tank was merely in the way, and sometimes the destruction of the tank is intentional, with the fish - always some deadly and often poisonous species - being used as weapons themselves.

Occasionally Played for Laughs in comedies, but this is rare. For the outdoor version, see Big Dam Plot.

Examples of Exploding Fishtanks include:

Anime and Manga

In an episode of Cardcaptor Sakura set at an aquarium, the Water card-spirit invades and causes just the sort of damage you'd expect.
DNA²

Commercials

Played for laughs in this Yellow Pages commercial.

Film

Martin Riggs intentionally shoots the aquarium in the office of Arjen Rudd, Minister of Diplomatic Affairs for the South African Consulate, Lethal Weapon 2.
Ethan Hunt blows up the floor-to-ceiling aquariums in a restaurant as cover for his escape in Mission Impossible.
The destruction of a very large (and thus very expensive) aquarium is the driving force behind the plot of Deuce Bigalow Male Gigolo, a rare comedy example.
In Total Recall, Diabolical Mastermind Vilos Cohaagen has an aquarium in his office. After he is forced to give the order to kill his brainwashed undercover best friend, he angrily kicks over the the aquarium. The shot of the fish gasping for air was a foreshadowing of the scene later in the movie where several characters are ejected onto the airless surface of Mars without pressure suits.
Octopussy. Octopussy is shown feeding her poisonous blue-ring octopus early in the film. Later, the aquarium is destroyed when James Bond rams an assassin's head into it (and said assassin ends up with the octopus wrapped around his face).
- Done in Licence to Kill in a scene appropriated from the novel Live and Let Die which was too cool to not be filmed.
In Push the screamers first makes the fish inside the tanks burst, and then the tanks themselves explode.
Happens in Rush Hour 2.
In the 2008 Speed Racer movie, the mob boss's piranha tank gets a single bullet hole, forcing one of the mobster underlings to sacrifice a finger to plug the hole.
Several shots are enough to crack an aquarium at a zoo in Eraser, which then explodes, covering the bad guys with water… And alligators.
Bizarrely averted in Gigli: a man is shot in the head with a large enough caliber gun to blow a chunk of brain out the back of his skull—and the chunk of brain lands in the undamaged fishtank behind him, leading to a lovely shot of fish nibbling at the thinkymeat.

Literature

Don't forget the aquarium with the huge Portuguese Man-of-War in Stormbreaker.
Happens with some very large fish tanks when Harry Dresden gets into a fight with some Denarians at an aquarium in Small Favor.
Early on in The Illuminatus!Trilogy an office building gets destroyed along with a whole shop full of rare fish.

Live Action TV

In The X-Files, Agent Mulder's fish tank never took any damage. The fish inside the tank, on the other hand...
This happened to Catherine Weaver's aquarium in The Sarah Connor Chronicles. It also revealed that her pet eel was a liquid metal construct, presumably a part of herself detached and used to keep an eye on her office when she wasn't there.
A narcissistic killer on one of the Law and Order programs poisoned his tank full of exotic saltwater fish when he fled his apartment, presumably so nobody else could ever enjoy having them.
It was a very bad idea to even think of damaging Sipowitz's fish tank in the squad room of NYPD Blue. So you can imagine his reaction when it was summarily taken out by a stray bullet from a rampaging perp.
CSI: NY had a guy who died when he fell into his aquarium, shattering it. No one knew until later that he was HIV positive, which created drama for Stella, who cut her hand while processing the scene.

Music Videos

The music video for Stupify by Disturbed has a recurring fish globe explode for no reason. Guitarist Dan Donegan mentions that they had a stunt-fish for different scenes.
The music video for "21 Guns" by Green Day has one in it

Toys

In Bionicle, Zaktan and the tank he was in are blown up by a sonic wave.

Video Games

The video game series, The Incredible Machine, includes aquarium objects. With few exceptions, if any moving object (such as a cat or a tennis ball) just touches one, the aquarium will explode spectacularly.
The intro of Jak X has Jak crashing through a fishtank with a car.
The player can do that in the first 'Splinter Cell.
In the Kowloon level of Call of Duty Black Ops, there is a room (apparently a kitchen) in one of the buildings, with 3 fishtanks. Considering the area is swarming with Spetsnaz, it is extremely likely the at least 1 tank will be shattered in the fighting.
Zork II hides a transparent object in a fish tank holding a sea serpent. The game makes sure you feel bad about the serpent dying in the open air once you break the tank.
Occurs in Enslaved: Odyssey to the West, and is actually used as symbolism/foreshadowing.
Happens when you destroy the entire aquarium in Spellcasting 301.

Western Animation

The comic version occurs in The Simpsons episode "Brother from the Same Planet" when Homer and Bart's 'bigger brother' Tom have a brawl in the aquarium. After the tank is shattered, they use the starfish as shuriken.