The fish’s fondness for the prawn cocktail-flavoured snacks had given it an unusually pinky hue – however, it should have been grey.

Baffled aquarists tried their hardest to encourage the fish, named Gerty, to feed – until they learned of her previous unorthodox diet.

“I have never heard of a fish being fed crisps,” said Curator Jamie Oliver. “Gouramis usually eat a diet of fruit and vegetation, but fortunately Gerty doesn’t appear to have suffered any ill effects from her unhealthy addiction. However, we would not recommend feeding fish crisps of any kind!”

Gerty is not the only unusual creature to come from private owners, which highlights a more serious issue.

Aquarists have nicknamed one display the ‘tank busters’ tank, because it houses a number of large fish that simply grew too big for their owners to manage.

“Many people don’t do the right research when they buy fish and end up unable to care for them,” continues Oliver. “Catfish are a good example, and we have a number here that outgrew their homes. Terrapins are another – they can live for 40 years and are actually quite costly to care for.”