Remember Sea Monkey's? Well, those were actually brine shrimp or, Artemia. Brine shrimp are used around the world for raising larval marine fishes.
Unfortunately, Artemia grow very quickly and their nutritional content changes as they grow. Newly hatched Artemia nauplii have a high fat content, 12-32%. By the time the nauplii reach pre-adult stage the fat content is down to under 10%. On the other hand, protein content increases from around 40% to over 60% in pre-adults. Keeping this information in mind will help you determine what size Artemia is needed at various stages of development. Larval fishes need a food source with a higher fat content than juvenile and adult fishes.
Another important factor to keep in mind is the size of the Artemia that are being used. As mentioned above, Artemia grow very quickly. For that reason, only newly hatched Artemia nauplii that are less than 12 hours old should be used during the transition from rotifers to larger foods.
Newly hatched Artemia nauplii do not begin feeding until they are 12 hours old so enrichment is difficult, if not impossible. When larger Artemia are needed they can be enriched with a HUFA supplement in the same manner as rotifers in order to provide proper nutrition.
Providing the proper sized Artemia nauplii for an extended time can be kind of tricky but I'll try to make it as simple as possible.
Culturing Artemia nauplii
Brine shrimp produce encysted eggs that can last for years when dried. You have a few choices when culturing your own Artemia.
1) Dried Artemia cysts can be found in vials at most any LFS at a reasonable cost. Dried Artemia cysts need to be hydrated, hatched, and separated from their shells before being used. This process can take 18 to 48 hours since not all cysts will hatch at the same time.
2) Decapsulated cysts are also available from various sources (See the resource page) but are a bit more expensive. Decapsulated cysts will usually hatch in 12-24 hours.
3) Or, you can decapsulate your own. This is the route I prefer, although I may be switching over to decapsulated cysts to save time.
My Method for Decapsulation
First, let me mention that decapsulation is a rather strange term. You're actually dissolving the shell with this process. If the cysts are allowed to hatch normally the shells are left behind.
In general, bleach is used to dissolve the shells. There are many more complicated methods for decapsulating that may produce a higher hatch rate, but this is the one I use for daily hatching and harvesting.
Things you'll need:
Brine shrimp cysts
53 micron strainer
Step 1: Fill a juice glass 1/4 full with common bleach and add the amount of dried brine shrimp cysts that you expect to need for the following day.
Step 2: Stir the cysts gently for about 10 minutes. The cysts will change color from brown, to white, to bright orange. When the process is complete the cysts will be bright orange and most will sink to the bottom of the glass.
Step 3: Pour into the 53 micron strainer and rinse with fresh water until you no longer smell bleach.
Step 4: Just to be safe, neutralize the bleach by rinsing with vinegar.
Step 5: Rinse with fresh water again.
Step 6: Using salt water, back flush the eggs out of the strainer into a hatching vessel such as an inverted soda bottle.
Step 7: Place the hatching vessel near a bright light and place a rigid air line inside to aerate the eggs and keep them moving.
Step 8: 12-18 hours later, remove the rigid air line and let the unhatched eggs settle. At this point the Artemia nauplii that have hatched should be swimming and can be harvested for use. By letting the unhatched eggs settle before harvesting the unhatched nauplii will sink and hatch later during the day.
Step 9: Replace the water that was siphoned out and replace the airline. Harvest again in 4 hours.
It's really not that difficult. It just looks that way when written down. The most important thing is to have a continuous supply of nauplii ready each day. I find that if I decap in the evening I will have nauplii hatching in time for the first feeding on the next day.
If you don't use all of the nauplii you can put them in a larger container and grow them out to use for larger fish.
Notes on Enrichment
I won't get into the enrichment process here, it's covered in the rotifer section.
When it comes time to use larger Artemia that need enriching it's very important to remember to rinse them after enrichinment with fresh water. Rinsing them will remove the excess fatty acids that can polute the larval rearing tank.