The ducks are to eat more healthily in 2014, according to Wollongong City Council, by ditching high-carb bread snacks.

Botanic Garden curator Paul Tracey said staff had been monitoring the ducks' diet and had noticed a lot of excess bread in the bottom of their pond.

"They were just being overfed. People were bringing in way too much bread," he said.

"We wanted to come up with a practical way for people to still enjoy feeding the ducks, but in a safer way."

Visitors have been advised to ditch sandwiches in favour of defrosted frozen peas or worms.

Mr Tracey said the switch would help reduce the chance of the ducks contracting diseases associated with a high-carb diet.

Signs have been installed in the garden to educate visitors.

"We want to encourage people to bring in healthier snacks," he said.

"Staff will take an educational approach and tell people there are better food options," Mr Tracey said.