They can be hatched out from an egg or dormant cyst as required and on-grown to different sizes. These are a popular food source as they can be enriched or gut loaded to enhance their nutritional profile.   

Artemia has been used as a live food for fish culture since the 1920’s; Over 85% of all marine fish cultured now have Artemia included in the diet during the early stages of life.

To understand how to culture any form of zooplankton it is first important to understand the basic biology of the animal you intend on culturing.

Brine shrimp do not live in the oceans.  They inhabit inland salt lakes. When the salinity in these lakes is high, the artemia lay a cyst (a dormant egg enclosed by a hard shell called the Chorion) rather than an egg, these cysts can lay dormant on the sides of the lake until the salinity reaches a desirable level for hatching. They can remain dormant for many years.

Artemia are predominately found in salt lakes where the salinity can vary from 10 parts per thousand to 180 parts per thousand. They prefer a salinity of around 35 parts per thousand.  In some places like the Great Salt Lakes in Utah, they collect these cysts, dehydrate them and put them into tins ready for sale. These cysts can be purchased from your Local Pet Shop in two forms : As cysts (dehydrated- still with the hard cyst shell) Or as decapsulated (hard cyst shell removed) ready to hatch.

Once these cysts are re-hydrated and the salinity is a suitable level for them to live, this triggers a hatching response.

The hatching usually begins at about the 15-20 hour stage (depending on hatching conditions).  They hang onto their egg casing for a few more hours until the embryo has finished developing (often called the Umbrella Stage).

From there at about the 24 hour mark, they have developed two appendages (swimming legs), antennae and an eye spot and are ready to be harvested.

They are now called Instar I nauplii. They have no mouth or anus as they are still developing.  At this stage they have a egg yolk reserve to aid them through the next stage of development.  This makes them highly nutritious for some fish fry. They can not be enriched or gut loaded at this stage because they are not developed enough to eat.  They also have no mouth or anus. 

Day 2 (approx 12 hours later) they begin to molt into the second larval stage called Instar II nauplii, they have a mouth and anus and a immature digestive tract.

During the next 15-30 days they molt and grow new appendages (swimming legs) with each molt, until they have reached adult stage.

The males can be clearly recognised now by their graspers, which are modified antennae near the head, while females should be starting to show a egg pouch near the tail. They will be an average size of about 8-10mm. 

Adults can live up to four months if kept in optimum keeping conditions.  If kept at low salinities (30-35 ppt) females can produce free-swimming nauplii (baby brine shrimp), in preference to the dormant cysts.

There are several parameters that will effect the hatching, growth rates and survival of artemia (brine shrimp), although they can tolerate quite vast water quality conditions and will survive in fresh water for up to 4-5 hours, they do grow and hatch best when kept as close as possible to optimum keeping requirements. These are all covered later in the sections hatching, enriching and on-growing. 

Factors that can cause your culture to crash are: over population, causing low oxygen levels,  over feeding creating high levels of dissolved nutrients resulting in poor water quality, bottom and floating debris hampering movement and therefore ingestion and starvation—lack of food.  

The higher the stocking density in the culture tank—the more maintenance. In highly stocked tanks it is recommended to use microalgae cultures in preference to inert foods as water quality is easier to maintain.  Adult artemia should be stocked at a rate of 1 per ml while newly hatched can be stocked at much higher rates of 100 per ml. 

Artemia are attracted to light, if your lights are too bright they will increase their swimming activity, they will use more energy and their growth rate will be slower, while lower light levels allow a slower swimming action increasing the conversion of food sources.  

Artemia are non-selective filter feeders and will eat a large variety of foods.  Food size is the main critical factor in food selection and should be approx 50-60 µm (microns) in size.  They do not possess a stomach—but instead have a gut line or intestinal tract, they eat continuously and therefore thrive when fed small feeds often.  

The food is not directly consumed, but instead forced by the action of the swimming legs, which have small bristles on them, which catch and force the food to an area near the mouth.  Glands excrete an adhesive that will clump this food matter into a small ball, it is then eaten from there. The movement of these swimming legs plays a critical role in ingestion of the food source and is why tanks need to be free of debris. 

Although the best foods are microalgae ( eg. Nannochloropsis, Dunaliella, Tetraselmis and Isochrysis), inert foods similar to spray dried algae (powders or pastes), yeast, micronised rice bran, soybean powder, ground fishmeal, egg yolk etc can also be used.  

To get the appropriate food size with the inert foods you can blend in a household blender for 4-5 minutes with some seawater. For the first few days while their digestive tract is developing they must be fed lightly.   

When newly hatched, Instar I nauplii are high in fat content, they still maintain a yolk sac, and for many fish fry species this is ideal.  The fat content begins to decrease as they grow and by adult stage they are higher in protein than fat.  If not fed 24 hours after hatching, their nutritional value begins to reduce.  Ideally fish fry need higher fat content in the early stages of life and as they get older their need for protein increases.   

The nutritional profile of brine shrimp can be enhanced by “enrichment” or “Gut Loading” .  Newly hatched artemia (Instar II) take approximately 18-24 hours to be fully enriched, while adults need only 6-8 hours.  Medium sized vary between 10-14 hours.

Why? 

The dehydrated shell is usually put through a process called decapsulation: removal of the hard outer shell. These cysts are often referred to as decapped cysts. 

The cyst must be re-hydrated prior to decapsulation. This is done by simply adding your cysts to water for about 2 hours. Adequate aeration is required during this re-hydration period to ensure the cysts stay in the water column. 

The cyst (brine shrimp egg) have several layers: first is the chorion—this is the hard outer shell that protects it during its dormant periods.  The only way to remove this shell is by oxidation with hypochlorite solutions—such as bleach. 

The second layer: the outer cuticular membrane allows movement of small molecules. While the third layer Embryonic cuticle is the hatching membrane we are left with after decapping, this membrane is the one they hang onto during the final stages of hatching. 

There are several reasons why decapping is commonly done: 

• The hard cyst shell (chorion) is not digestible and can lodge in the gut of small fish fry causing obstructions – this nearly always results in death. 

• Cysts shells can be contaminated with bacteria and pathogens, this procedure disinfects them and eliminates these problems.

• Separation after hatching of the hard shell and the live brine is a very tedious and frustrating job. After decapping the hatch is cleaner.

• The hatch time is usually slightly shorter and the hatching percentage rates are significantly higher.  

How? 

It easier to decap a larger amount than needed and then store them for future use. Because you usually purchase your cysts in a dehydrated form, they must be re-hydrated before you can decap them. 

To do this, they are placed in some water (tap water is fine), aeration needs to be added to keep them circulating in the water column. 

After about 2 hours your cysts should look nicely rounded.  

The following example will allow you to hatch out 10 grams of dehydrated cysts—one well-rounded tablespoon is approximately 10 grams of dry weight dehydrated cysts. 

It is very important to have all of your equipment ready before you start the procedure.  Time can be critical and once that bleach starts to work, you will not have time to go off and start looking for things you forgot, your decap could be past the point of no return by the time you get back. 

Hygiene of hatching vessels is critical.  After each procedure, decapping, hatching, enrichment, etc it is necessary that the hatching container be cleaned thoroughly and  rinsed in warm water.  

You will need:  

Note:  If you cannot get hold of Soidum Thiosulphate, which is used to de-chlorinate or stop the bleach working, then you can rinse your cysts for about 10-15 minutes and get the same results.  You must however rinse until there is no chlorine smell left at all. 

How to make 0.1M  Sodium Thiosulphate

Add 24.8 grams (approx 1 rounded tablespoon) of Sodium Thiosulphate per litre. Tap water is used to make this mixture.  Slightly warming the water will help the sodium thiosulphate crystals to dissolve. You may need to purchase this product from a chemical supply store.

Step 1.

Re-hydration of Cysts: Remember these cysts will be dehydrated and for a successful decap, they must be hydrated. 

Add cysts to the water, and aerate for about 2 hours.  Keep your air steady and not too vigorous as the cysts will end up on the sides of your hatching vessel and will not re-hydrate properly.  

You can check them under a magnifying glass to ensure they are all nicely rounded.  It is important to note that they are a brown colour at this stage of the procedure. 

Step 2.

The decapping process should take approximately 7-8 minutes, you will need to watch them the entire time, to ensure they are removed from the solution before they can be harmed. 

If you want to, you can add a couple of cubes of ice to the vessel now to ensure the temperature rise does not harm the cysts.  

Add your Hypochlorite solution and ensure all your cysts are being kept within the water column, not splashing up the sides of your container. If the aeration is too vigorous the solution can foam and trap cysts in this foam and they may not decap properly. 

Step 3.

Your cysts will start to change from a brown colour to a white colour, I use a small pipette and take a look them every minute to watch the colour change occur.

Step 4.

From white they will begin to turn orange.  It is at this stage the procedure is nearly finished.  When the majority (about 90-95%) of the cysts are an orange colour you are ready to rinse them. 

Step 5.

Remember at this stage the bleach is still working so it is important to have everything ready that you will need and the de-chlorination needs to be done as quickly as possible. 

If no de-chlorination solution is available, the cysts need to be rinsed with tap water, through a fine screen (105µm is preferred) or a very fine net.   This can take 10-15 minutes before the smell of chlorine is no longer present. 

If you have sodium thiosulphate (de-chlorinator) available now is the time use it. The soidum thiosulphate will deactivate the chlorine process immediately, let them sit in the solution for a minute or so, until there is no smell of chlorine.   

The cysts then need to be rinsed again in tap water to remove any sodium thiosulphate residue from them. The cysts can then be left for about 10-15 minutes to allow the excess water to drain away. The cysts are now ready for hatching or dehydrating for long-term storage. 

Remember that the weight of your cysts has changed! Dehydrated cysts straight from tin contain 0% moisture, decapsulated cysts contain about 70% moisture and dehydrated, decapsulated cysts contain about 43% moisture.  

This is important because when you weigh you cysts to hatch your cysts at a rate of 2 grams per litre of water you have to make allowance for this moisture. For example 1 teaspoon of dry weight equals about 2 grams, decapsulated cysts equals 6 grams and dehydrated, decaped cysts equal 3.5 grams.  

The following chart will help you work out what your cysts now weigh and how much the moisture content is.                               

Short Term Storage of Decapped Artemia Cysts

Place the drained cysts in the fridge in an air-tight container for use within 2 weeks. 

Long-term Storage of Decapped Artemia Cysts

Cysts can be dehydrated and stored in a saturated brine solution in the fridge—they can be kept this way for several months. 

To achieve this we need to make a saturated brine solution.  Using tap water add salt (cooking salt is fine) at the rate of 350g/litre of tap water.  This needs to be mixed over the period of several days to ensure most of the salt crystals have dissolved.  A small amount crystals should remain after mixing. 

Using a vessel similar to the hatching vessel (clean and rinsed well, prior to use) add 1 litre of saturated brine solution to the decapped cysts, aerate gently for approximately 1 ¹/₂ hours, turn off the air and let the cysts settle, pour off the saturated brine solution, being careful not to pour away your cysts.  Add some fresh saturated brine solution and again aerate for approximately 1 ¹/₂ hours. 

Turn off aeration and let the cysts settle again and pour off excess saturated brine solution.  Place these dehydrated, decapped cysts into an airtight container and top up with fresh saturated brine solution. 

These cysts can now be stored for up to three months.  When you wish to hatch your cysts, spoon out the required amount and place into a small container (cup size is fine), fill to the top with tap water, leave to settle for several minutes and pour off the water, repeat this process for about 3—4 times prior to hatching.   

This will slowly begin the re-hydration process which must occur before the cysts hatch.  Because the cysts have been dehydrated the hatch time will take longer, 8-12  hours longer, the cysts will need to be re-hydrated before they can begin to hatch. 

 25-28°C (77-82°F) For hatching

24 hour bright light for hatching (50-100 lux)

The aeration should be vigorous and keep the cysts moving in the water column for the duration of the hatching.  During the hatching time the pH of the hatching water will drop considerably.  It is advisable to not let it get below 7.5.   

If this happens you may want to make an adjustment. To increase the pH to a higher level that will increase your chances of a better hatch rate an adjustment using Bi-carb soda can be added at the rate of 1/4 teaspoon per 2 litres. 

At approximately the 18 hour mark, turn off aeration and hold a torch to the side of the container and you should be able to observe the Instar I hatched artemia, often called newly hatched brine shrimp. If most of the cysts are hatched, you are ready to rinse them through a screen.  If however, there are still many un-hatched cysts then you may need to allow the cysts up to 6 hours longer to hatch properly. 

An easy way of ensuring there is no debris with your artemia is to darken off the upper part of your container, add a strong light near the side of bottle after about 5-10 minutes all the nauplii will be attracted to the light, while the debris and unhatched cysts fall to the bottom. 

If your hatching vessel has a bottom drain, you can drain off this debris carefully, then begin to drain artemia nauplii until all are in a screen or net (105 µm—micron), remembering to only drain off half the water. If you leave this sit for a further 5-10 minutes with the light, a second harvest can be made ensuring you have most of the cysts.

There are several other ways to harvest the cysts if you do not have a bottom draining vessel, a siphon hose is another way—you miss the bottom debris and only get the swimming hatched artemia. Because they are attracted to the light they will congregate near the light you have placed at the side of the tank.  

These hatched artemia are now referred to as Instar I artemia (or newly hatched brine shrimp). They still have a yolk sac and are only just starting to develop a digestive tract, they are unsuitable for feed to seahorse fry at this stage, they can however be fed to some fish fry. 

This is the time to either enrich or gut load your newly hatched artemia or add them to a grow out tank.  Your artemia will continue to moult and grow new appendages, they should reach adult hood after about 15 moults or 3 weeks.

Artemia Enrichment - Enrichment or Gut Loading of Artemia 
The nutritional profile of artemia can be altered with the use of micro-algae and specially formulated enrichments like DC Super Selco®.   To increase the nutritional value they are enriched or gut loaded with essential components such as highly unsaturated fatty acids. Instar II and Instar III rapidly lose weight and nutritional value and must be fed.  Starving nauplii have little or no nutritional value at all. 

Ideally fish fry need higher fat content in the early stages of life and as they get older their need for protein increases.  Newly hatched artemia (Instar II) take approximately 18-24 hours to be fully enriched, while adults need only 6-8 hours.  Medium sized vary between 10-14 hours. 

Enrichment—DC Super Selco® from INVE Aquaculture is an excellent preferred enrichment. Enrichment can be done in the cut-off inverted plastic bottles used for hatching at a rate of 1/8 teaspoon Selco per litre of water for 2-3 grams of newly hatched artemia.  

This should be blended for 3-5 minutes also.  Optimum temperature for enrichment is around 25°C (77°F).   

Prior to feeding out artemia should be placed in appropriate size screen (105 µ - micron for newly hatched artemia) and rinsed in tap water for several minutes.  Enrichment products can deteriorate water quality in tanks so it should be rinsed off prior to feed. 

Although the DC in Super Selco® stands for disinfects continuously it is best to be cautious and rinse all foods prior to feeding to your seahorses, either in tap water or clean sea water.  If there are any bacteria you will dilute it to minimal proportions by rising. 

Hygiene is a priority, all containers used must be rinsed prior to use, washed with hot soapy water after use and rinsed thoroughly afterwards. 

On-growing of Artemia

When on-growing artemia it is best to use a conical shaped container with a central airline (do not use air stones– large air bubbles are preferable).  Oxygen levels should exceed 2 mg/litre, pH should be maintained between 8-9, levels below or above can be lethal. 

Optimum Levels for On-growing:

30-35 ppt

There are several parameters that will effect the growth and survival of artemia (brine shrimp), although they can tolerate quite vast water quality conditions and will survive in fresh water for up to 4-5 hours, they do best when kept as close as possible to optimum keeping requirements for on-growing.

Factors that can cause your culture to crash are: over population, causing low oxygen levels, over feeding creating high levels of dissolved nutrients resulting in poor water quality, bottom and floating debris hampering movement and therefore ingestion and starvation—lack of food.

The higher the stocking density in the culture tank—the more maintenance. In highly stocked tanks it is recommended to use microalgae cultures in preference to inert foods as water quality is easier to maintain. Adult artemia should be stocked at a rate of 1 per ml while newly hatched can be stocked at much higher rates of 100 per ml.

Artemia are attracted to light, if your lights are too bright they will increase their swimming activity, they will use more energy and their growth rate will be slower while lower light levels allow a slower swimming action increasing conversion of food sources.

Artemia are non-selective filter feeders and will eat a large variety of foods. Food size is the main critical factor in food selection and should be approx 50-60 µm (microns) in size.

Remember, they do not possess a stomach—but instead have a gut line or intestinal tract, they eat continuously and therefore thrive when fed small feeds often.

Although the best foods are microalgae ( eg. Nannochloropsis, Dunaliella, Tetraselmis and Isochrysis), inert foods similar to spray dried algae (powders or pastes), yeast, micronised rice bran, soybean powder, ground fishmeal, egg yolk etc can also be used.

When newly hatched, Instar I nauplii are high in fat content, they still maintain a yolk sac, and for many fish fry species this is ideal. The fat content begins to decrease as they grow and by adult stage they are higher in protein than fat. If not fed 24 hours after hatching, their nutritional value begins to reduce.

Keeping all parameters close to seawater levels aids growth. Artemia can tolerate quite high levels of ammonia, although this is not highly recommended. Water changes weekly can aid with water quality.

Artemia should be fed 2 times daily, small feeds often works better than one large feed daily. Feed at about 1/4 spoon of inert feed each day to each 10 litres of water. To ensure you are not overfeeding, let the water almost become nearly transparent before adding any more food.

Remember also that newly hatched artemia do not have a well developed digestive tract and are still learning to eat, light feed for the first few days, and then increase the amount of food offered.

Each day it is a good idea to turn the airline off and let the debris settle either swirl and bottom drain conical containers or siphon flat bottom containers while artemia swim near surface. Replace any water taken out from cleaning and this will give a small water change each day to your artemia tank.

This aids with water quality and ensures artemia don’t get caught in any floating debris. Artemia should reach adult size and begin mating within 3-4 weeks.

If you are feeding algae you will find that most of the particles will be the perfect size for your artemia to eat immediately, however if you are using an inert food or a spray dried algae paste or powder you will need to break down the particles to make them small enough for the artemia to eat.

The easiest way to do this is to add the amount you are feeding to about 1 cup of sea water, add this to a regular household blender and blend for approximately 3-5 minutes. This can then be added to your grow-out tank.

There are several brands of spray dried algae and foods available on the market. Your local health shop should sell Spirulina in powder or tablet form, you can crush the tablets up into a powder and add to water to blend. Your local aquarium shop may also sell some of these spray dried powders or foods.

It is a good idea to give your artemia grow-out tanks a 100% water change each week, and give your grow-out tank a good wash in tap water. Run your water through an appropriate screen size to ensure you don’t lose any, rinse thoroughly in tap water and then add to clean on-growing container.

Recommended screen sizes for rinsing and harvesting artemia are:
Newly hatched 105 µm - micron
One Week old 105-150 µm - micron
Two Week Old 150–200 µm - micron
Three Week Old 200-500 µm - micron

Temperature Conversions

°F

°C = °F — 32

        1.8  

°F = 1.8 x °C + 32

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