Brine Shrimp (Artemia salina). Live brine shrimp are one of the three just about ubiquitous live foods available at the LFS. Yes, they are really shrimp— fairy shrimp (Anostraca), to be more precise, a division of the crustaceans. The "eggs" (they're really cysts) hatch into free-swimming nauplii (Nauplios, "the navigator," sailed with the Argonauts), which molt several times on their way to becoming adults. The newly-hatched nauplii are standard first food for larger fish fry, like cichlids and a major step forward along the live food sequence in raising the smaller fry, like anabantoids, tetras and barbs. Brine shrimp are a handy source of roughage, which is provided by the chitin in their shells; chitinous roughage is especially important for those purely carnivorous fishes that won't touch plant matter.
Artemia come from environments so briny that few other organisms survive, places like the Great Salt Lake and some salt pans at the south end of San Francisco Bay. Wild populations in salt lakes of Saskatchewan haven't been commercially exploited. Wind and currents mass the floating cysts in drifts at shorelines, where collectors ladle them out. In the Great Salt Lake artemia feed on salt-tolerant bacteria and cyanobacteria, and when their population periodically crashes, there's a temporary population boom of brine flies that feed on the dead artemia. Quite a simplified ecosystem in such a spectacularly harsh environment! In the 1990s, at the same time as Utahn shrimp-collecting became concentrated in a handful of consortiums, whose main market in fact was aquaculture in the Far East, not US fishkeepers, Great Salt Lake declined as a dependable source for brine shrimp and their cysts, through drought cycles made worse by human interventions. In turn, Chinese commercial sources expanded, culturing Artemia in salt pans in the Bohai Sea, the northernmost arm of the Yellow Sea, which separates China from Korea; there the sun-dried cysts are packed in vacuum-sealed canisters and soft packets. There are also Artemia industries in Taiwan and Brazil.
When you rinse brine shrimp and release them in freshwater, did you ever notice how the little buggers react by diving towards the bottom? There's survival value in this hard-wired behavior, which is a reaction to lowered salt levels. Normally the Great Salt Lake is all but saturated with sodium chloride and other salts. But each year, for a few short weeks following snowmelt, vast quantities of freshwater come pouring out of the Wasatch Mountains into the Great Salt Lake. Since freshwater is lighter than brine, the snowmelt forms a temporary freshwater "lens" floating on the surface waters. When salt concentration drops below about twice the brininess of seawater, to less than 70ppt, the cysts hatch. A harsh evolutionary selection process awaits any Artemia that don't make it down to the briny layer; they soon die by the gazillions from osmotic shock. (The annual rain of dead brine shrimp, precipitating out, as it were, on the alkaline mud substrate, is part of the exotic nutrient cycle of this extreme environment. But that's another story.)
Since Artemia live in such briny places, people sometimes assume that brine shrimp must be rather salty themselves. In fact the salt is on the outside. Drop the artemia that collect at the bottom of the net into a cup of fresh water and drain them again in the net before feeding them to the fish. Within their shells, the body tissues of artemia are only a very little saltier than the meat of a freshwater shrimp.
Because of their briny native haunts, Artemia are absolutely guaranteed not to introduce any parasites into a freshwater system. (And especially not the osmotically-challenged hydra, current urban myth to the contrary notwithstanding.) Generally speaking, our fears of introducing parasites with live food are exaggerated, it appears, even with the two most widely-maligned imagined offenders, tubifex and blackworms. But be careful not to feed brine shrimp that have died in their brine; they go bad very quickly indeed.
Storing live brine shrimp. When you buy live brine shrimp, don't expect to hold them for more than a few days. If you can keep them cold in the refrigerator, their metabolisms will slow, they'll stay alive longer, and they'll retain more of their nutritional value. (Starving brine shrimp aren't as nutritious as well-fed ones.) I maintain higher pH levels for the Artemia with some crushed coral in their pan. Take-out food sometimes comes in a wide pan with a clear plastic cover that I like, since it provides space for perhaps an inch of brine with maximal surface area and the cover cuts down on evaporation. This is handier and more effective than running aeration through the brine.
Hatching brine shrimp. The price of dry brine shrimp cysts has ballooned since about 1990, so that people have turned increasingly to microworms. Still, hatching brine shrimp nauplii to feed the fry has been one of the traditional rituals of spawning aquarium fishes ever since they were first identified as a prime food for fry in the 1930s.
Those brine shrimp "eggs" in the canister at your LFS have been sitting on the shelf at room temperature for how long, do you suppose? Premium quality cysts, with a high guaranteed hatch-out rate, are the way to go, as long as you're committed to preserving the quality you're paying for by keeping the ones for current use under refrigeration and keeping those for future use in the freezer. The on-line leader in premium Artemia cysts is BrineShrimpDirect; they maintain an informative website.
Storage of the cysts. Top quality Artemia salina cysts have a hatching rate of 90%. To preserve a high hatching rate for the brine shrimp "eggs" you have to store them carefully. Heat and damp are their enemies; until recently I thought that you can't let them freeze: I was misinformed. So keep the brine shrimp eggs in the fridge or freezer, in a tightly-sealed container. Enclose one of those plastic containers of desiccant that come in pill bottles. Some commercial sources also include a packet of an oxygen adsorbent, to cut down on oxidation. And if you aren't currently using the cysts regularly, you might even seal the cap with masking tape. If you mark the outside of the can "Brine Shrimp Eggs" everyone in the family will be much happier. That old vial of brine shrimp eggs at the back of your fish cabinet? You can probably discard it! Do a test hatching, but expect that its hatching percentage is way down by now.
Unhatched cysts. The unhatched cysts and fragments of the shells are dangerously indigestible. They've been known to block the minute digestive tracts of fry, resulting in sad mortalities. So interrupt the aeration and let detritus clear away before you siphon off nauplii from mid-water levels.
Success in hatching Artemia cysts. Hatching brine shrimp successfully depends on five factors: salinity (1.015-1.020 specific gravity), the pH (high; a pinch of Epsom salts, which is magnesium sulfate, and a pinch of baking soda, which is sodium bicarbonate, could raise pH and help buffering in soft water), temperature (80-82o is ideal), at least half an hour of bright light (part of the hatching trigger) and gentle aeration (which keeps the cysts in gentle motion and prevents unhatched cysts from settling to the rapidly developing low-oxygen zone at the bottom). Aeration should be gentle, not vigorous. Avoid an airstone (it would rapidly clog, anyway), since fine bubbles may trap the nauplii with surface tension. If you are constantly re-culturing brine shrimp, bacteria may build up in your equipment, causing losses to the nauplii. You can sterilize with household bleach, if you rinse well and let it dry. I see hydrogen peroxide recommended, as it leaves no salty residue, but it's much more expensive.
The ideal hatching container was identified in the 1970s as a cylinder with a funnel-shaped bottom. Aquarists quickly adapted plastic litre soda bottles, with the bottoms cut off and inverted into a stand formed from the bottle base. Sacrificing a second bottle will give you a sturdier, deeper base and a taller hatchery that reduces the amount of salt spray from the areation. A good way to survey the various DIY projects is to set your google to "Images" or open YouTube and search "Brine Shrimp hatchery".
Separating the nauplii from the floating unhatched cysts and thetwo- indigestible shells that sink to the bottom, once aeration is turned off, requires some dexterity. A plastic drinking straw with your finger over the end makes a useful dip-tube. Light attracts the nauplii, and some systems use it to concentrate them before siphoning them into a fine-mesh net.
"Incomplete" nutrition? The food value of brine shrimp is currently denigrated as incomplete, according to some sources, but you aren't restricting your fishes to any diet that consists of a single food, live or not, are you? What is involved, it now appears, is DHA (decosahexanoic acid), but the marine fishes are the ones that can't synthesize it, not our freshwater fishes, which do have a limited ability to synthesize DHA from a certain fatty acid. I mention this because you'll hear a lot about brine shrimp and "incomplete" nutrition, parroted from reefkeepers. The general agreement is that newly-hatched nauplii ("baby brine shrimp" or "bbs") use up their initial food reserves during their first twelve to twenty-fours hours: while the nauplii are still feeding on their yolk reserves their nutritional value is at its highest. After that, the increasingly starved nauplii are much less nutritious for your fish fry. More specifically, Artemia don't begin to feed until after their second molt. Brine shrimp nauplii begin life rich in "good" fats and in the long-chain highly unsaturated fatty acids (HUFAs). Various fatty acids are precursors— building blocks— of fish tissues, of hormones and other elements of the immune system. Some fatty acids have to be taken in from the diet, because the fish cannot manufacture them.
The nutritional value of newly-hatched brine shrimp nauplii, once they have reached the feeding stage, and of the adults, can be improved by keeping them in a brine enriched with Selcon, which stands for "Self-Emulsified Liquid Concentrate." This technique is called "bio-enrichment". Bio-enrichment formulas like Selcon are "high HUFA" formulas. Essentially what's involved is some fish oil, such as cod liver oil, that's been whipped together with an emulsifying agent, like lecithin. If you needed lots of the stuff at a low price, you could do this yourself; but you can get Selcon from a stylish LFS (it's a good test of an unfamiliar LFS) or from several on-line distributors. Cichlid fry raised using Selcon-enriched brine shrimp are claimed to have brighter permanent color. I can't vouch for this from personal experience, but I pass it on to you. If you plan to give the brine shrimp a last Selcon meal, take a tip from the witch in Hansel and Gretel, and fatten up only those that you are about feed to the fish. After about two hours in enriched brine, they'll have taken in as much Selcon as they're going to. In a longer bath, what goes in just passes out. Discard the enriched brine.
In a similar manner, brine shrimp can become a vehicle for getting medications into the intestinal tracts of your fishes, not an easy task, for freshwater fishes hardly drink at all. This new "bio-encapsulation" technique is similar to bio-enrichment.
Raising brine shrimp to maturity? What? are you completely mad? A handful of fanatics take matters a step further and raise brine shrimp to maturity. The process requires saltwater rich with green algae and has always sounded daunting to me. A lot of experienced fishkeepers will tell you to concentrate your energies on raising daphnia instead.
Difficulties in culturing Artemia to maturity, which takes two to three weeks, are emphasized at www.brineshrimpdirect.com. Their article "Brine shrimp in the classroom" is also interesting.
Brine shrimp links. Before you undertake hatching your own brine shrimp, take Kai Schumann's brine shrimp seminar, "Artemia FAQ 2.0".
Then, go directly to the site of BrineShrimpDirect for a look at the FAQs at this site. These are the best, simplest hatching tips I've found on the web. Here you'll also find techniques for "decapsulation," in which you partly dissolve the cysts in order to increase the hatching rate. The technique involves a solution of household bleach and, to halt the reaction, a solution of sodium hydroxide you mix yourself, or sodium thiosulfate (de-chlorinator). Not something I've done myself, I might add. But it's good to hear about this stuff.
There are good hatching techniques also at Adrian Tappin's "Home of the Rainbowfish" site.