Invertebrates

Brine Shrimp

Artemia · also called sea monkeys, Artemia

Least Concern → filter feederomnivore Rivers & wetlands Coasts & shorelines

A brine shrimp is a centimetre-long crustacean that lives in water too salty for almost anything else, swims upside down, and filters algae for a living. It is famous for two things: its eggs, which can be dried out and stored for decades and still hatch, and the fact that those eggs were sold to millions of children as Sea-Monkeys.

Overview

Brine shrimp are the genus Artemia, tiny filter-feeding crustaceans of salt lakes and salt pans worldwide — the Great Salt Lake, San Francisco Bay salt ponds, desert salt lakes. They live in water several times saltier than the sea, which frees them from nearly all predators, so their numbers can be vast. They swim on their backs, toward light, rowing with eleven pairs of legs, and some populations are all female.

Eggs that wait for years

When conditions worsen, a female makes cysts — dormant embryos that can be dried completely, frozen, even exposed to vacuum, stored for decades, and then hatch within a day in salt water. This survival state is called cryptobiosis.

Fish food and a novelty

Because the cysts store on a shelf and hatch to order into a swimming, nutritious first food, newly hatched brine shrimp are the near-universal starter feed for aquarium and farmed fish and shrimp larvae. The same cysts, packaged with cartoon art of crowned humanoids, became the mail-order Sea-Monkeys in 1957.

Status

Least Concern as a group. But the Great Salt Lake population — the source of most of the world’s harvested cysts and the main food of millions of migratory birds — is threatened as river diversions shrink the lake and push its salinity past even what brine shrimp can survive.

Brine Shrimp: common questions

Are sea monkeys real animals?

Yes. Sea-Monkeys are brine shrimp, specifically a hybrid brine shrimp bred for the novelty market, sold as dried cysts that hatch when added to salt water. Everything in the packet is genuine, the eggs, the salt, and a water conditioner, and the animals really do hatch, grow, swim, and breed. What is not real is the marketing image. The classic Sea-Monkeys advertising shows pink humanoid creatures with crowns and webbed hands and feet, which brine shrimp do not resemble in the slightest, being translucent, elongated, many-legged crustaceans a centimetre or so long. The name was coined because the tail was thought to look a bit like a monkey's.

How can brine shrimp eggs survive for years?

The eggs are not really eggs in the everyday sense but cysts, which are embryos that have developed to an early stage and then shut down almost all metabolic activity and lost most of their water, entering a state called cryptobiosis, meaning hidden life. In this dried, dormant condition the embryo produces protective sugars and proteins that stabilise its cells, and it can withstand being fully desiccated, frozen to near absolute zero, boiled briefly, exposed to the vacuum of space, and irradiated, all of which would kill an active animal. When the cyst is returned to warm salt water it rehydrates and the embryo resumes development, hatching within about 24 hours. Cysts have remained viable after more than 20 years of dry storage.

Why are brine shrimp used to feed fish?

They tick every box for a live first food. The cysts can be bought in a tin, kept on a shelf indefinitely, and hatched in a day into thousands of tiny swimming shrimp exactly when a batch of fish larvae needs feeding, so there is no need to maintain a live culture. Newly hatched brine shrimp are the right size for most small fish larvae, they are highly nutritious, being rich in protein and, at hatching, in energy-dense yolk, their swimming movement triggers a feeding response in the fish, and they stay alive in fresh water long enough to be eaten rather than fouling the tank. Almost every aquarium fish breeder and marine fish and shrimp hatchery relies on them.

Is the Great Salt Lake brine shrimp population in trouble?

It is under real pressure. The Great Salt Lake supplies most of the brine shrimp cysts harvested commercially for the world aquaculture industry, and it is also the key food source for millions of migratory birds such as eared grebes and phalaropes that stop there to feed. Decades of diverting the rivers that feed the lake for irrigation and urban water supply have caused the lake to shrink and its salinity to climb, and if salinity rises much further it will exceed even the brine shrimp's tolerance, causing the population to crash. That would end the cyst fishery and pull the bottom out of the lake's food web. Efforts are under way in Utah to get more water to the lake, but the trend has been downward.

Sources & further reading

Written by HideShark Editorial Team · reviewed by HideShark Science Desk. Published September 10, 2026. Last updated September 10, 2026.

Quick facts

Scientific name: Artemia
Diet: A non-selective filter feeder that beats its leaf-like legs to draw a current of water past the body and strain out single-celled algae, bacteria, and tiny organic particles, and in the extreme salt lakes where it lives there is often little else in the water but the microbes it eats
It lives where almost nothing else can: Brine shrimp thrive in water several times saltier than the sea, up to and beyond the point where salt starts to crystallise, in places like the Great Salt Lake, San Francisco Bay salt ponds, and desert salt lakes, and this tolerance frees them from nearly all predators and competitors, so their numbers can be enormous
Eggs that survive drying and freezing: When conditions turn bad, a female produces cysts, tough-shelled dormant embryos that can be dried completely, frozen, exposed to a vacuum, and stored for years or decades, then hatch within a day of being placed in salt water, a survival state called cryptobiosis
The sea monkey: In 1957 the cyst trade was turned into a mail-order novelty marketed as Sea-Monkeys, complete with cartoon drawings of humanoid creatures, and generations of children have hatched brine shrimp from a packet, watched them grow, and been disappointed that they do not look like the picture
A standard laboratory and hatchery animal: Because the cysts can be stored on a shelf and hatched to order into a swimming, nutritious first food, newly hatched brine shrimp are the near-universal starter feed for the larvae of aquarium fish and of farmed fish and shrimp, and the animal is also widely used in toxicity testing
It swims upside down toward light: A brine shrimp swims on its back, rowing with its eleven pairs of legs, and it moves toward light, a behaviour hatcheries exploit by shining a lamp at one side of a hatching cone to concentrate the shrimp for collection away from the empty shells
Some populations are all female: Several brine shrimp populations reproduce by parthenogenesis, with females producing more females without males, while others reproduce sexually, and the different lineages vary in salt tolerance, size, and cyst quality, which matters to the companies that harvest wild cysts for the aquaculture industry
Range: Salt lakes, coastal salt pans, and solar salt-production ponds worldwide except Antarctica, wherever water is much saltier than the sea and stays warm enough for at least part of the year, with major populations in the Great Salt Lake of Utah, the salt ponds of San Francisco Bay, the Mediterranean and Middle Eastern salterns, and inland salt lakes across Asia, Africa, and the Americas.
Conservation status: Least Concern → ≈ Brine shrimp as a group are not threatened, being abundant in salt lakes and salterns around the world and further spread by the aquaculture trade, though individual salt-lake populations are vulnerable to the loss of their water. The Great Salt Lake population, the source of most of the world's harvested brine shrimp cysts, has come under pressure as river diversions for farming and cities drop the lake level and raise the salinity past even what brine shrimp can tolerate, which would collapse the fishery and remove the main food of millions of migratory birds. In several regions native Artemia are also being displaced by introduced American brine shrimp in the wild