The marine aquarium hobby looks little like it did when it first became popularized decades ago. Nowadays, it might seem as though a new fad emerges every month. Yet, a few things seem to never change. One such undying custom is the use of brine shrimp (Artemia sp.) as a food for aquarium fish—freshwater and brackish as well as saltwater. As reef aquarium keeping becomes more commonplace, these hardy little crustaceans are increasingly being used as a diet for filter-feeding zooplanktivorous invertebrates (e.g. many corals). To this day, brine shrimp are used to grow out the majority (over 85% according to some sources) of cultured marine species. Given their substantial importance in the aquarium hobby/industry, it is of advantage to any aquarist to know a little about their natural history.
What are brine shrimp?
First of all, brine shrimp are not shrimp at all. They belong to the class Branchiopoda and the order Anostraca. Artemia is the only genus in the family Artemiidae. It remains mainly unchanged since the Triassic period. Though not particularly abundant in the wild, they are distributed worldwide.
Artemia could easily survive in a relatively comfortable habitat such as a coral reef or open ocean. However, because they are terribly slow swimmers, they would be quickly preyed to oblivion by the many deft zooplanktivores that also live there. Consequently, brine shrimp have adapted to life in the harsh (but comparatively predator-free) environment of inland salt lakes. Populations of brine shrimp can persist in these sometimes unlivable places owing to the animal’s ability to produce durable, dormant eggs (i.e. cysts). Because of its tough outer capsule, a cyst can survive punishing extremes of temperature and salinity.
The bread and butter of captive fish
Brine shrimp have been harvested for use as a feed for aquatic animals since the 1920s. The annual Artemia harvest has been steadily increasing over time. Each year, over a 1,000 metric tons of brine shrimp are harvested from sites in the U.S., Canada and France, most of which is immediately frozen as a prepared food for the pet and aquaculture trades. To be sure, this business appears to be growing still. You could indeed almost say that feeding brine shrimp (whether live or frozen) has become standard practice amongst marine aquarium hobbyists. And there are certainly some very good reasons for its widespread use. Just a few of these include:
– They have a rather broad larvae-to-adult size range, making them useful as feed for a wide variety of fish and invertebrates.
– Their chitinous exoskeletons act as dietary roughage, thereby promoting digestive tract health in diverse animal groups.
– They have a protein content that is high enough to support normal growth and development in most marine species.
Live Artemia are tolerant of a variety of environmental conditions, and so can (1) ship easily with minimal mortality and (2) survive in any kind of aquarium for a long enough amount of time to be found and consumed. Perhaps unsurprisingly, there are some reasons to select live brine shrimp products over frozen alternatives. These include:
– Live Artemia swim in a motion that is irresistible to most fish, and so can be used to elicit a feeding response from recently imported or especially finicky specimens.
– Because they are slow swimmers, they are easily captured by slow-swimming fish such as seahorses.
– Live products have a generally broader and richer nutritional content than frozen products.
– Live products are less likely to foul the aquarium water than frozen products.
Alright, so when it comes to brine shrimp, live is best. So are all live shrimp products the same? The answer simply is no. There are a few important differences between different live brine shrimp feeds. Most notably:
– Captive-hatched is preferable to wild-hatched.
– Young individuals are preferable to adults.
– Newly hatched feed should be obtained from decapsulated cysts.
When packaged in a clean, bio-secure environment, captive-hatched live products are far less likely to introduce contaminants, parasites or fouling organisms into an aquarium than their wild counterparts. Also, captive-hatched products can be obtained at younger ages. This is especially important, since very young individuals (i.e. nauplii) are overall more wholesome. This is due mainly to their comparatively high fat content, which ranges from 12-32% of the dry weight. However, fat content drops rapidly after hatching—down to 16.5% by the time individuals reach 2.5mm in length. This is mainly why it is best to obtain freshly hatched product.
Nutritional value will be somewhat higher in product that has been hatched from decapsulated cysts. This is because each young individual has used up less of its endogenous energy reserve (i.e. yolk sac) while breaking out of its shell. Decapsulation additionally makes the product safer, as the shell fragments from untreated cysts (which are indigestible) can clog the guts of some animals. Moreover, the decapsulation process completely sterilizes the cysts, making them completely disease-free. Untreated Artemia cysts are, for example, a known source of bacterial infection (e.g. Vibrio). If properly decapsulated, even the unhatched cysts can serve as a safe and nourishing food source.
Because only a premium live brine shrimp product will do
Any aquarist can benefit from making live brine shrimp a major part of their captive animals’ diets. With all of the above considerations in mind, most will fare best using a quality live product such as Nano Brine. For one, the cysts used to produce Nano Brine are carefully decapsulated and thus (1) exhibit the highest hatch rates, (2) are free of pathogens, (3) are maximally nutritious and (4) are safe for all species to eat. Best of all, packaging of the cysts used in Nano Brine is timed such that the product hatches just before arrival at your door, guaranteeing a nutritionally optimal feed. Now that Nano Brine is readily available through subscription, aquarists need not suffer the messes made or time consumed decapsulating, hatching and harvesting their own Artemia week after week. It’s really as simple as pouring a bag of delicious, healthful goodness into your reef!
 Hoff, Frank H. and Terry W. Snell. Plankton Culture Manual. 6th ed. Dade City, FL: Florida Aqua Farms, Inc., 1987.