After diving into the warm sea off the coast of northern Bali, Indonesia, Made Partiana hovers above a bed of coral, holding his breath and scanning for flashes of movement. Hours later, exhausted, he returns to a rocky beach, towing plastic bags filled with his exquisite quarry: tropical fish of all shades and shapes. "I started as a fisherman in 1997, after elementary school, because my parents could not afford my education. So at that time I became an ornamental fisherman," said Partiana. Millions of saltwater fish like these are caught in Indonesia and other countries every year to fill aquariums in living rooms, waiting rooms and restaurants around the world with vivid, otherworldly life. But the journey from places like Bali to Rhode Island is perilous for the fish and the reefs they come from. Some are captured using squirts of cyanide to stun them. Many die along the way. Even when captured carefully, by people like Partiana, experts say the global demand for these fish is contributing to the degradation of delicate coral ecosystems. "The sea is big and has open access.So, we can use it as long as we don't use cyanide, we respect nature and we are catching fish with nets – which are environmentally friendly," said Partiana. There have been efforts to reduce destructive practices, such as cyanide fishing. But the trade is difficult to regulate and track as it stretches from small scale fisherman in villages through middlemen, export warehouses, international trade hubs and finally to pet stores in the U.S., China, Europe and elsewhere. "Most of the fish coming to the US are legally acquired. But there is a proportion of fish that come into the United States, and we don't know what that proportion is that are certainly illegal and they're intermixed together. It's not possible for the even the person who's importing them to know which fish are being collected properly and which fish are not," said Andrew Rhyne, a marine biology professor at Roger Williams University in Rhode Island. Most ornamental saltwater fish species are caught in the wild because breeding them in captivity can be expensive, difficult and often impossible. Nearly 3 million homes in the U.S. keep saltwater fish as pets, according to a 2021-2022 American Pet Products Association survey. About 7.6 million saltwater fish are imported into the U.S. every year. For decades, a common fishing technique has involved cyanide, with dire consequences for fish and marine ecosystems. Fishermen crush the pellets into a bottle filled with water. The diluted cyanide forms a poisonous mixture fishermen squirt onto coral reefs, where fish usually hide. The fish become temporarily stunned, allowing them to be picked from the coral. Many die in transit, weakened by the cyanide – which means even more fish need to be captured to meet demand. The chemicals damage the living coral and make it difficult for new coral to grow. Cyanide fishing has been banned in countries such as Indonesia and the Philippines, but enforcement of the law remains difficult, and experts say the practice continues. "If a fish is caught with cyanide or in an area that's prohibited, then then the fish would be illegal. But it's not possible for the consumer to really know which fish is which because they don't have a tag like your clothes have on them that tell you where they come from," said Rhyne. Another obstacle to monitoring and regulating of the trade is the quick pace that the fish can move between locations, making it difficult to trace their origins. At a fish export warehouse in Denpasar, Bali, thousands of fish a day can be delivered in white Styrofoam coolers crammed with plastic bags of fish from around the archipelago. The fish are swiftly unpacked, sorted into tanks or new plastic bags and given fresh sea water. Ones that died in transit are thrown in the trash. Some fish will remain in small rectangular tanks in the warehouse for weeks, while others are shipped out quickly, fulfilling orders from the U.S., Europe and elsewhere. Once the fish fly from Indonesia to the U.S., they're checked by the Fish and Wildlife Service, which cross-references the shipment with customs declaration forms. But that's designed to ensure no protected fish are being imported. The process cannot determine if the fish were caught legally. A U.S. law known as the Lacey Act bans trafficking in fish, wildlife, or plants that were illegally taken, possessed, transported, or sold – according to the laws in the country of origin or sale. That means that any fish caught using cyanide in a country where it's prohibited would be illegal to import or sell in the U.S. But no test exists to provide accurate results on whether a fish has been caught with cyanide. " When it comes down to it, the onus is on the importer. The importer is the one that needs to pick the exporter that is doing the right doing. You know, exporting animals correctly, complying with their nation's export laws and wildlife conservation laws as well," says Carlos Pages, an officer at the U.S. Fish and Wildlife Service. In the absence of national enforcement, conservation groups and local fishermen have have long been working to reduce cyanide fishing in places like Les, a saltwater aquarium fishing town in northern Bali. Partiana started catching fish – using cyanide -- shortly after elementary school, when his parents could no longer afford to pay for his education. Every catch would help provide a few dollars of income for his family. But over the years Partiana began to notice the reef was changing. Experts say it this type of local education and training that should be expanded to reduce harmful fishing. In Rhode Island, Jack Siravo, a fish enthusiast, shares Partiana's hopes for a more environmentally friendly saltwater aquarium industry. "You learn the effect of collecting," he says. "I don't want fish that are not collected sustainably, because I won't be able to get fish tomorrow if I buy fish today."