Goldfish memory proven to last nearly a week.

Goldfish appear to have the ability to remember certain things for nearly a week.

An Australian teenager has busted the myth that goldfish have only a three-second memory, proving that they have mental capacities to learn and remember complex concepts and retain knowledge for at least six days.

Fifteen-year-old Rory Stokes, from the Australian Science and Mathematics School in Adelaide, taught a small group of fish to swim to a beacon by establishing a memory connection between the beacon and food.

After the initial three-week period, the beacon was removed from the feeding process.

Six days later, the beacon was again placed in the water and it was noted the fish quickly swam to the beacon despite not seeing it for almost a week, showing they had remembered the association between food and the beacon.

"We are told that a goldfish has a memory span of less than three seconds and that no matter how small its tank is, it will always discover new places and objects," Rory said.

Stokes told reporters his findings prove it is cruel to keep fish in small tanks.