In the Animal Crossing series, fish can be placed in the player's house as furniture. When placed, they come in their own fish tank. Unlike Bug Cages where the lid color varies on the value of the bug inside, there is no visible variation in the tank except for decoration. In earlier games fish tanks were nearly identical, but in City Folk they were all updated with more detail and varying bases which range from sand and gravel to dirt.
There are three sizes of fish tank: 1x1 (small fish), 2x1 (large fish) and 2x2 (very large fish). Goldfish do not live in tanks, and swim in a blue-rimmed bowl with seaweed and only the smallest fish tanks (1x1) can be placed on tables, excluding in City Folk. Sea horses and sea butterflies live in a small, cylindrical tank that the player can place on tables.