In the original release of The Sims, the only way Sims could have any sort of pet was to have the Poseidon's Adventure Aquarium. As long as the fish were fed daily, and the tank was kept clean, the fish would live indefinitely. The Hot Date and Superstar expansions added large 1x2 aquariums, but these were purely decorative and did not require maintenance.
Aquariums are lots of fun. Well at least for some people. Just don't forget to feed the fish and clean the tank periodically, and they will swim happily in circles forever.
Required pack(s): none
The Sims 2Edit
In The Sims 2 base game, the only way Sims could have any sort of pet was to have the Aquabox Five-Gallon Aquarium. The Pets expansion pack added a 1x3 saltwater aquarium called Mr. Maritime, and changed aquariums so that cats could watch them. When bought, these aquariums are empty, and can be stocked by clicking on them and selecting the "Restock" option. Stocking the Aquabox costs §35, while stocking Mr. Maritime costs §300, and Sims may stock them autonomously. The fish must be fed every 48 hours, or they will die. They can be fed more often, but this will make the tank need to be cleaned more often.
Unlike The Sims, Sims in The Sims 2 will not react when fish in an aquarium die, and the game will not give the player any notice that the fish have died. When told to restock the aquarium, Sims will scoop the fish out of the tank, take them to what they consider the nearest toilet, and flush them away, then return to the tank and add new fish, for which they will be charged.
Apartment Life added a large 4x4 aquarium, which was primarily decorative and did not require maintenance, although Sims and cats could still watch it.
The Sims 3Edit
In The Sims and The Sims 2, aquarium fish were not separate objects. In The Sims 3, however, they are. Fish can be caught by fishing in ponds, rivers, lakes or oceans and placed in bowls or tanks. A bowl holds one fish; an aquarium holds six, which allows fish to reproduce.
If fish are not fed daily, death music will play and the fish will die of starvation (although the Grim Reaper doesn't come). In some games, the fish tank can also turn green to warn the player that the fish need feeding.