On the outskirts of Sydney, in a fast-growing suburb is a model of future farms, growing organic herbs and fish.

Green Camel has taken a good idea — to recycle water from aquaculture to hydroponics — and improved on it, spending millions of dollars on developing secret technology.

It all starts in small gurgling tanks where fingerlings of barramundi dart about, growing at an astounding nine per cent of their bodyweight every day.

Within seven months, the fish are 30 centimetres long, weighing 800 grams and ready for the live-fish trade into Chinese restaurants.

This is intensive food production, where as on the storey above conveyer belts of herbs move slowly but grow fast, in the regulated warmth and sunlight of this 5,000 square metre greenhouse.

Green Camel has ironed out its issues since a consortium of investors took over the business several years ago and is now in the black, producing 130,000 kilograms of herbs and 15,000 kilograms of fish a year.

Green Camel general manager Levi Nupponen has trained one thousand University of Sydney students in the operation, but has kept it largely out of the public spotlight until now.

Live barramundi are fed from fingerling to 800 grams for the live restaurant trade in Sydney, and water is recycled and used to grow organic herbs upstairs in the greenhouse. ( Supplied )

Live barramundi for Sydney restaurants

Barramundi are highly efficient feed converters.

"Here we get a wet food conversion ratio of about 0.9 to 1. For every 900 grams we feed these fish, we get one kilogram of saleable fish out the other side.

How does that compare to other meat?

"Probably the most productive terrestrial protein is chicken and that's about 1.8 to 1 so for every 1.8 kilogram you put in, you get one kilogram of chicken out the other side," Mr Nupponen said.

"This is about 200 per cent more efficient [than chicken]."

As with any intensive livestock production, you have to deal with faeces.

"In a small system like ours, which is 180,000 litres, you would discharge somewhere in the order of 20,000 to 40,000 litres of nutrient rich water to the environment every day," he said.

Fingerling barramundi gain 9 per cent of their body weight every day, until they reach 800g for the live restaurant trade in Sydney. ( Sarina Locke )

"This would mean you can't produce near a city and you'd be adding nutrients to the environment, which are toxic."

The system, which is still secret, filters and reuses 100 per cent of the waste.

"So every piece of faecal matter and every drop of water that the fish produce, we take that, we convert that into usable solutions and grow the crops above," he said.

That is using each drop of water twice, either water caught on the roof, or city mains water.

"So we use tanks full of bacteria, which convert the ammonia into nitrate," Mr Nupponen said.

Upstairs inside this greenhouse are rows of herbs such as basil and coriander.

"We've got a moving gully system, so that means they're only touched by human hands once when they're planted, they move onto a conveyer belt, spaced out to optimal density for harvest," he said.

"They'll arrive 90 metres away to be touched by human hands for only the second time when harvested."

The 5000m2 greenhouse grows high-value organic herbs, watered by recycled and treated water from aquaculture. ( Supplied )

Levi Nuppnen said the greenhouse on the south-west fringe of Sydney could produce 15,000 kilograms of barramundi and 130,000 kilograms of leafy greens a year on just 5,000 square metres of land.

"Every drop of water is accountable, every single joule of sunlight as well," he said.

"We measure everything from the first ray of sunshine to the last drop of water we use before the sunset. We know what it gets converted to and what we can produce from it.

"We use all that water to grow the fish, then every single drop used to grow the fish is used to grow the crops."