Did a quick search on goldfish memory and came up wiht this juicy tidbit in the Nakedscientistforum:
"You've got the memory of a goldfish" - Sorry, it's no longer the insult it used to be !
Indeed, recent work on fish learning and behaviour has refuted the long standing myth that goldfish are intellectually destitute. Far from being like Dory in "Finding Nemo" (who was condemned to a life of rediscovering the delights of the surroundings every few seconds) fish actually have extremely good memories.
In a recent series of experiments, Edinburgh University fish researcher Culum Brown (Animal Cognition 4 pp109) showed that Australian freshwater rainbowfish could rapidly be trained to locate an escape-hole in a fishing net as it was advanced towards them. The fish were then not tested again until 11 months later - at which point they could still remember how to perform the task as effectively as they had in the past - despite not having seen the apparatus in the meantime.
This is clear evidence that fish have a well developed capacity for learning and recall of information up to a considerable time later.
The 'three second memory' myth should therefore be laid firmly to rest !