Tanks 1-4 have five levels but tank 5 has only a level in which a player must beat the final boss in order to complete the game. In adventure mode, a player advances through five tanks. Insaniquarium can be played in Adventure, Time Trial, or Challenge mode.

The deluxe version of Insaniquarium contains eight different aliens, but in the original Java version there are four. The aliens must be clicked on repeatedly with the mouse pointer in order to defeat them. In addition to feeding fish, the player must protect the fish from aliens that periodically enter the tank and attempt to eat the fish. Each creature must be kept alive by feeding, whether through fish food bought by the player or other species of fish in the tank. Guppies and other fish drop money, which can be collected by the player and used to purchase fish food and upgrades, such as more filling food and powerful lasers to repel attackers. Players must manage a tank of guppies and other aquatic creatures, each stage begins with two guppies in the tank or one breeder which creates guppies. Player uses the mouse to feed fish and fight aliens The latest version, Insaniquarium Deluxe, was released in September 2004 for PC. Shortly after, a PDA version was released.

During development a member of the team purchased a goldfish and examined its movements and behaviour. The first version of the game, developed by Flying Bear Entertainment, is Java-based and available as a free online game.

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