Australia's largest barramundi farm is harvesting plate-size fish, ready for market, out of its new ponds.

Last year, Humpty Doo Barramundi outside Darwin, built 10 new growing ponds in an effort to double the farm's production over the next three years.

Given the significant expansion and nine months of work to grow the barramundi, the farm's Laura Van Ryswyk said seeing the first harvest of the new ponds was very exciting.

"It was a big expansion and it is a big accomplishment, so it is really exciting," she said.

The Humpty Doo Barramundi crew harvest the fish by pulling the net through the pond and pumping the fish into large slurry bins. ( ABC Rural: Lydia Burton )

The fish were due to be harvested in May but in an effort to meet the growing demand for plate-size fish, they were left a little longer to grow larger before being harvested.

"These plate-size fish are about 600 grams to one kilogram in size," Ms Van Ryswyk said.

"They will be sent all over Australia — Adelaide, Melbourne fish market, Sydney fish market, some will even go to Perth."

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Originally, it was thought the farm would produce 50 tonne of barramundi a week with the expansion.

"We are pretty close; we are at about 35 to 40 tonnes a week at the moment," Ms Van Ryswyk said.

"They arrived on the farm in October so it is about nine months of age for the plate-size fish and 18-24 months for the fillet fish."

Ms Van Ryswyk said there were plans to expand the farm further.

"We have got nine more ponds being built," she said.

"Also, a stage three nursery facility to be built so that we can grow our fingerlings to an even bigger size before we stock them into the ponds."