New Zealand green-lipped mussels are large and delicious. They feed on nutrients that wash off the hills surrounding the mussel farms, and aren't given any chemicals or supplements whatsoever. The mussels and surrounding water are checked weekly for bacteria, biotoxins and acidity.
We visited a mussel farm in the Marlborough Sounds, on the South Island of New Zealand. We were privileged to go on a mussel boat with Gary, a local mussel farmer who supplies Sandford South Island, one of the larger mussel co-ops in New Zealand. The mussel-growing process and the economics of it are fascinating; mussels are apparently the cheapest form of protein available, as well as being grown free of any chemical additives.