Background. Two types of brine shrimp occur in Australia- artemia and parartemia. Artemia occur worldwide, and in Australia are around man-made saltworks. Parartemia occur in inland salt lakes. In a salt waterhole off the Strezlecki Track, I have seen the water red, and scooped a litre of shrimp in minutes.

Artemia. Artemia is used in the aquarium hobby and commercially. The artemia are able to cope with a large range of salinities, - far more than their predators. They will grow in temperatures between 6 and 35 degrees Celcius, but I have found the best for my purposes to be around 27 to 28 degrees Celcius. The female produces eggs which hatch into free-swimming nauplii. Under perfect conditions, these can mature into adults in 8 days and produce 300 nauplii every 4 days. Under severe conditions, eg high salinity caused by the waterhole drying up, the female lays about 75 cysts.These are eggs covered with brown chorion which has air channels for buoyancy. These cysts are blown ashore where they are collected commercially. The embryo within stays in a state of dormancy until the right conditions are met.

Hatching. (at 28 degrees Celcius)

0 hours. The cysts can only be kept for long periods if kept dry. More than 5% moisture, and their shelf life is greatly reduced. When viewed under a magnifying glass, the eggs have a dimpled or concave appearance.

2 hours. When added to water, the eggs swell with the intake of water. If light is present, the hatching process begins.

15 hours. Breakout. Within the embryo is a compound which swells with the addition of the water inside the egg. After 15 hours, this increasing pressure breaks the cyst's shell.

20 hours. The embryo, still in its membrane, hangs below the shell.

24 hours. Hatching. The nauplii develops an enzyme which softens the membrane. This enzyme needs a PH of about 8. The free-swimming nauplii (called Instar 1), has a large yolk reserve and cannot feed.

36 hours. The nauplii now moults, and is called Instar 2. The yolk reserve is almost gone, and it has one-third less food value than Instar 1. It now commences to eat.

Next 8 days. The nauplii moults another 15 times befor reaching adulthood.

Quality. Different strains of artemia hatch at various sizes. Also the highly unsaturated fatty acid (HUFA) varies. Obviously the more hufa content the better.

Hatching conditions.

1. 25 to 28 degrees Celcius

2. 5 to 35 ppt salinity. I use seawater or if lazy, use an exact amount of swimming pool salt. One fistful per half litre of fresh water!

3. PH 8. If using freshwater, add some sodium bicarbonate - 1 teaspoon per litre.

4. Density. I use 1 teaspooneggs per container. Recommended is no more than 5 g/litre.

5.Light. Subdued light is OK and is even better for decapsulated cysts.To be perfect, 1000 to 2000 lux, or 100 lux for decapsulated.

6. Aeration. At the rates I use, very high aeration is a must.

Nuts and Bolts. To make a conical funnel:- My favourite containers are plastic 1.25 litre plastic coke bottles. I cut the bottom off, turn it upside down. I put some airline hose through the lid, sealing it with silastic glue. If I am using normal eggs, this tubing protrudes about 1 cm above the lid. I put a couple of holes high up in the side and attach some wire to hang the bottle on the wall. The tubing is brought back to a cuphook in the wall higher than the bottle. The tubing is cut and a joiner put in the tube. From here it goes to the air supply. 1. Half-fill the bottle with water. If using fresh water, put in a fistful of coarse salt ( or a couple of tablespoons). The varying salinity of each batch does not seem to affect the hatch rate. 2. Add some eggs according to your needs. (4 bottles rotation morning and night, 1 teaspoon in each were what I needed for 5000 Oscar fry). 3.After one and a half days, disconnect the tubing for 5 minutes. The brine shrimp are phototropic (attracted to light), so they swim towards the neck of the bottle where the light is concentrated. The tubing is then lowered into a container covered with fine mesh, e.g. handkerchief. The nauplii are caught, while the alt water flows through. The empty cysts have either an air bubble in them which floats them out of the way on the surface, or they have sunk below the protruding air hose. 4. Rinse the nauplii with fresh water, then feed to the fry. Notes. I don't harvest all the brine shrimp at the one time. I feed the fry 5 times a day.

Note. Because of the release of compounds into the water during the hatching process and bacteria on the chorion (shells), a high level of bacteria is attained. Make sure the nauplii is rinsed before feeding them to your fry. Many hatcheries decapsulate the cysts first to reduce this hazard.

For decapsulated cysts, the tubing in the coke bottle can be flush with the lid.

1. Place cysts in the coke bottle and add FRESH water. Aerate well for 2 hours. Add chlorine at rate of 22g/L active chlorine (see note)

2. In 7 to 10 minutes, the colour will change from brown to white to orange.

3. Immediately remove the eggs and rinse them with running water. Alternatively, place them in a solution of sodium thiosulphate (chlorine neutralizer) for 1 minute, then rinse them under running water.

4. Now ready to be hatched as before.

5. Storage. The drained decapsulated eggs can be kept for 2 days in the refrigerator.

6. Longer storage up to 3 months. Add 350 g salt to fresh water. Add decapsulated embryos. Aerate gently for 3 hours. (The concentrated salt solution will dehydrate the eggs). Drain eggs and put in a new saturated salt in a number of bottles. These will now be ready for use.

Notes. Decapsulation removes bacteria. Take note that the decapsulation process creates heat, and if the temperature exceeds 40 degrees Celcius, the embryos will die. Some hatcheries use a lower rate of chlorine and consequently a longer time to decapsulate (up to 40 minutes). My chlorine concentration was never constant as it varied with the age of the chlorine and I suspect the concentration may have varied when I bought it. I used liquid chlorine from a swimming pool supplier.

The nutritional value of brine shrimp can be enriched, especially HUFA (highly unsaturated fatty acids).

There are commercial enrichment foods available, but I made up my own.

1. Feeding Algae. I used a tank of fresh water kept in sunlight .The water was green with algae. I added this water to the nauplii.

2. HUFA. Blend 5 parts cod liver oil to 1 part of egg yolk to 94 parts water. Add to nauplii. (Must be Instar 2 to be able to eat it.) The nauplii have become enriched from 6 to 12 hours. Thoroughly rinse the nauplii before feeding to the fry.

Storage. At room temperature, the nauplii quickly lose their enrichment. By holding them at under 10 degrees Celcius, they may be kept for 24 hours with minimal loss of enrichment.