Image copyright Nathalie Bertrams Image caption Agus Joko Supriyatno farmed sustainable coral until exports were banned

"After the ban, I lost everything," says Agus Joko Supriyatno. "It cost me my house, my wife and my health."

For years, the 52-year-old made his living as a cultivator of sustainable, farmed coral just off the coast of Nusa Lembongan, a small island near Bali.

But when the Indonesian government banned all coral exports in 2018 to stop illegal harvesting of wild coral, hundreds of sustainable farms across the country collapsed.

Mr Supriyatno had been supplying hundreds of pieces of coral per week to aquarium shops in Europe and China, where they are used in fish tanks for decoration.

But his underwater farm went bust, and he ended up suffering a stroke, which he says was caused by the stress.

Image copyright Nathalie Bertrams Image caption Mr Supriyatno grew his sustainable coral on racks on the sea bed

Now, he and other farmers are hoping to get their lives back on track after Indonesia's new Minister of Maritime Affairs, Edhy Prabowo, reversed the ban at the beginning of January.

But environmentalists fear that without a blanket ban, there will be a resurgence in illegal harvesting, as farmed and wild coral are often indistinguishable.

Coral is a living thing, groups of marine invertebrates that live together in compact colonies. It can either come from the wild, or be cultivated in underwater farms, such as Mr Supriyatno's.

Before the Indonesian ban it was perfectly legal to export the farmed variety, and the country was the world's largest supplier, accounting for 70% of the coral sold to the £13bn-£15bn global marine aquarium market.

But in 2018, Indonesia's former maritime minister, Susi Pudjiastuti, felt extreme measures were needed to stop overfishing and foreign poaching of wild coral in Indonesian waters.

She also thought it was too difficult to differentiate between farmed and wild coral, with the latter often being passed off as the former. And so she brought in a law that stopped coral exports of all kinds overnight.

Image copyright Nathalie Bertrams Image caption Indonesia was the world's largest supplier of farmed coral

According to one estimate, the move caused about 12,000 people across the Indonesian archipelago to lose their jobs. Among those hit were pet fish exporters such as Aqua First Bali, which says it has lost nearly three-quarters of its revenue over the past two years.

Manager Irwanto Suganda explains that importers in Europe and elsewhere "stopped buying our fish when coral was no longer part of the package". That is because importers often buy the two together to reduce the transportation costs.

Hardest hit were small coral cultivators like Mr Supriyatno, who usually live in coastal communities and depend entirely on their farms for income.

When his offshore nursery was operational, Mr Supriyatno employed a team of workers to handle the delicate job of tending the coral, which is grown on metal racks placed on the seabed, about one metre below the surface.

It requires diving down to brush the sensitive corals to clean them of algae, and pruning them regularly.

Image copyright Nathalie Bertrams Image caption Coral make popular additions to aquariums

After the 2018 ban came in, however, Mr Supriyatno wasn't able to pay the staff anymore, and had to let them go. Hundreds of racks of coral have been left untended, and are now smothered with algae, which is slowly suffocating them.

Since the government's U-turn in January, licences to export farmed coral are being issued once again, and Mr Supriyatno says he is seeking investors to help restart his once profitable business.

Explaining its decision last month, the government said it now wants to "promote" export activity under "good governance management", and recognised the economic benefit to the country.

But not everyone is happy with the shift, given that it risks the illegal removing of wild coral starting again. Coral reefs are both a breeding ground for commercially valuable fish and critically important for the preservation of the planet's biodiversity.

Image copyright Nathalie Bertrams Image caption A rise in tourism to Indonesia is partly to blame for the damage to the country's coral reefs

And in recent decades, a deadly cocktail of overfishing, tourism and climate change has destroyed more than a fifth of the world's reefs.

Indonesia, whose seas are rich in coral, has been particularly badly hit. A 2018 report from the Indonesian Institute of Sciences found that more than two-thirds of the reefs around the 17,000 islands of the Indonesian archipelago are severely damaged.

Dr Richard Thomas from Traffic, a non-governmental organisation campaigning to stop the illegal trade of wild animals and plants, says: "The challenge will be to ensure that any reopening of the farmed coral trade in Indonesia does not lead to a 'gold rush' on wild coral reefs."

While farmed coral may seem to be an ethical alternative, he says, there is "a real enforcement challenge here - that of distinguishing between what is genuinely farmed and what is wild-sourced".

Most coral species are protected by the Convention on International Trade in Endangered Species of Wild Fauna and Flora (Cites), which regulates international trade in endangered wildlife through quotas and import and export requirements. The agreement has been signed by more than 190 governments, including the UK and the European Union.

But Cites has previously failed to stop illegal harvesting of wild coral in Indonesia, as export quotas are often not properly monitored or enforced.

Image copyright Nathalie Bertrams Image caption Mr Supriyatno, pictured here with his children, hopes to restart his coral farm

Coral farmers like Mr Supriyatno say that by allowing the farmed coral trade to flourish, demand for wild coral will fall, curbing smuggling.

In 2017, the year before the ban, more than half of the 600,000 pieces of coral that were imported by the EU came from Indonesia. But with Fiji and Hawaii also having banned exports recently, global demand is outstripping supply.

It has led to a rising black market, with Indonesian smugglers shipping illegally harvested coral to nearby Singapore where they are relabelled and shipped on to Europe.

Small pieces of coral typically retail for between £20 and £50, but particularly large or colourful ones can cost as much as £4,600. "Demand is high, and for some it is worth every risk [to sell wild coral]," one Indonesian trader told the BBC on condition of anonymity.

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In fact, in the European Union in 2017, nearly half of all seizures of illegal coral, and the rocks on which it grows - a whopping 18,000kg - were from Indonesia.

In preparation for the end of Indonesia's ban on farmed exports, all registered coral farms were audited in December, and Ministry of Fisheries staff were trained to inspect shipments for export. But environmentalists will be watching closely to see that such oversight continues.

Mr Supriyatno is cautiously optimistic about his prospects, but remains wary. Many aspects of the reopening of the trade remain uncertain, and clear policies and guidelines are yet to be provided.

"I hope politicians will be wiser now," he says.