January 18, 2010
HOW TO RAISE BRINE SHRIMP (artemia) TO ADULTHOOD
HATCHING AND REARING ARTEMIA BRINE SHRIMP
FOR JACK DEMPSEY FRY
The common brine shrimp (artemia) is in the phylum Arthropoda, class Crustacea. Artemia are closely related to zooplankton like Copepods and Daphnia, which are also used for live food in the aquarium. The artemia life cycle begins by the hatching of dormant cysts which are encased embryos that are metabolically inactive. The cysts can remain dormant for many years as long as they are kept dry. When the cysts are placed back into salt water they are re-hydrated and resume their development. Artemia cysts are best stored in a tightly sealed container in a cool, dry environment. The refrigerator is usually best.
After 15 to 20 hours at 25 degrees C (77 degrees F) the cyst bursts and the embryo leaves the shell. For the first few hours, the embryo hangs beneath the cyst shell, still enclosed in a hatching membrane. This is called the Umbrella stage, during this stage the nauplius completes its development and emerges as a free swimming nauplii. In the first larval stage, the nauplii is a brownish orange color because of its yolk reserves, newly hatched artemia do not feed because their mouth and anus are not fully developed. Approximately 12 hours after hatch they molt into the second larval stage and they start filter feeding on particles of various microalgae, bacteria, and detritus. The nauplii will grow and progress through 15 molts before reaching adulthood in about 8 days. Adult artemia average about 8mm long, but can reach lengths up to 20mm in the right environment. An adult is 20 times longer in length, and a 500 times increase in biomass from the nauplii stage. In low salinity and optimal food levels, fertilized females usually produce free swimming nauplii at a rate of up to 75 nauplii per day. They will produce 10-11 broods over an average life cycle of 50 days. Under super ideal conditions, an adult artemia can live as long as three months and produce up to 300 nauplii or cysts every 4 days. Cyst production is induced by conditions of high salinity, and chronic food shortages with high oxygen fluctuations between day and night. Adults can tolerate brief exposures to temperatures as extreme as -18 to 40 degrees C (0-104 degrees F) Optimal temperature for cyst hatching and adult grow out is 25-30 degrees C (77-86 degrees F), but there are differences between strains, San Francisco bay strain is 22 degrees C as compared to 30 degrees C for Great Salt Lake. Artemia prefer a salinity of 30-35 ppt (1.0222-1.0260 density) and can live in fresh water for about 5 hours before they die. Caution should be used to not over feed in a fresh water aquarium because of the rapid decomposition of the dead. Many fresh water fish will tolerate and even thrive in a brackish water environment of 1-5 ppt easily, so it is possible to add saltwater to the tank and extend the survival of the artemia if required.
Other variables of importance are pH, light and oxygen. A ph of 8-9 is best; pH less than 5 and greater than 10 will kill the culture. the pH can be increased with baking soda, and lowered with muriatic acid. A minimum amount of light is necessary for hatching and may be beneficial for adult grow out. A standard grow lite bulb available in an aquarium supply is adequate. Most important is the level of oxygen in the water, as this dictates what the artemia will consume. With a good oxygen supply, the artemia are a pale pink or yellow, or if they are heavily feeding on microalgae they will look green in color. In this ideal condition growth and reproduction is rapid, and a self-sustaining artemia supply is possible. If there is a low oxygen level in the water with large amounts of organic matter, or a high amount of salinity from evaporation, the artemia will feed on bacteria, detritus and yeast cells, but no algae. It is under these conditions that they produce hemoglobin and look red or orange in color. If this environment remains they will start producing resting cysts, and the colony may crash. It is very important to have a vigorous air supply in the tank for two reasons, one is to keep the available food supply in suspension where it can be filtered out, and the other is to promote a good oxygen supply in the system. (in other words – a boiling cauldron is fine)
The optimal conditions for hatching artemia are as follows – 25 degrees C, salinity – 5ppt (1.0030 density), heavy continuous aeration, light – 2000 lux constant illumination, pH 8-9. Good circulation is essential to keep the cysts in suspension. A container that is V shaped is best (two liter bottles work good, the absolute best I’ve found are separation columns found in any lab supply – they’re expensive though). glue a valve on the cap and invert, this way unhatched cysts, empty shells, and hatched nauplii can be easily removed separately. Another idea I would highly recommend checking out was offered by Ken Cunningham (email@example.com). His discovery was to use pilsner beer glasses, Some of them have a conical point at the bottom, these are the ones to look for. Ken places three or four in a ten gallon tank and heats them by the water bath method. Put rigid air lines in the glasses with no air stones, connected by flexible tubing to the distribution manifold. 80 degrees, bright light at all times. In each glass put 1/2 teaspoon of salt, 1/2 or 1/4 teaspoon of cysts, and bubble for 24 hours. To harvest, leave the rigid tubing in the glass, but lift it out of the aquarium and disconnect the flexible air tube at the manifold. Let the glass settle in relative darkness (i.e. not bright light) for 10 minutes, and siphon the artemia out using the airline tubing into fresh water to rinse. By using the glasses on a rotation, its possible to have hatched artemia available at all times. Still another good idea comes from Wright Huntley (firstname.lastname@example.org) who originally got the idea from Oleg Kiselev. Wright now uses Chianti wine bottles found at Trader Joes for 4 bucks. By tilting the bottles on edge and using the same salt and cyst ratio as Ken, quite high hatch rates are being obtained. harvesting is the same, by siphoning using the air tubing, but into a funnel lined with a handkerchief, then the artemia may be rinsed if desired, and fed. There are many methods in use for hatching these guys. Once you play with whatever particular method you chose to achieve optimum performance, your results will probably be just as good as any other hatching method. Dont be afraid to experiment.
The hatching percentage and density are usually a function of water quality and circulation. Containers with flat bottoms have dead areas in the corners and are not ideal for maximum hatch rates. It doesn’t take alot of cysts to get going, there are usually 200,000 to 300,000 nauplii per gram of cysts, so a half teaspoon in a two liter bottle is more than enough for the typical aquarist. With a setup of two or more bottles, one started one day, the other the next, you can have a continuous supply of newly hatched artemia for that reef tank every day.
Harvest the nauplii by turning off the air, or remove the air stone, and let the culture settle for about ten minutes. Hatched, empty shells float to the surface, and unhatched cysts will sink to the bottom. The newly hatched nauplii will concentrate just above the unhatched cysts on the bottom. Since the newly hatched nauplii are attracted to light (phototropic), by shining a flashlight at the center of the bottle, you can concentrate them where it is easy to siphon them off, or drain the cysts off the bottom by using the valve, then drain the nauplii onto another container. The unhatched cysts should be used in the next culture and not thrown away, most of the time they will hatch with the next batch.
Since artemia are non-selective filter feeders (meaning they dont care what they pick out of the water), a wide range of food has been successfully used. The criteria for food selection should be based on particle size, digestibility, and solubility (powdered milk wont work). Feeds that have been used include live microalgae such as nanochloropsis and a wide variety of inert foods, which are far more practical for us aquarists. One caveat with inert foods is to be careful not to overfeed. Inert feeds include yeasts, both active and inactive (a brewers supply is the best source, bread yeast is expensive!) micronized rice bran, whey, wheat flour, soybean powder, fish meal, egg yolk, and homogenized liver. Dried microalgae such as spirulina has also been used with success (available from health food stores, but again kind of expensive). The simplest way to measure food levels in the tank is by figuring the transparency of the water. This is done with a dowel with measuring marks marked off in centimeters, and a white disk glued on the end. The depth where the white disk just disappears measures the light penetration into the tank. The more stuff floating around the tank, the less transparency. With a stocking density of 5000 nauplii per liter, the transparency should be 15-20 cm the first week, and 20-25 cm thereafter. Of course it is best to maintain an optimal food level at all times, so frequent feedings, or better yet, a continuous drip feeding are mandatory for optimal grow out.
Food is not directly consumed, but rather transferred to the mouth in a packaged form. The space between an artemias legs widens as the legs move forward. Water is sucked into this space from below, and small filtering hairs collect particles including food from the incoming stream. On the back stroke the water is forced out and the food remains in a groove at the base of the legs, this groove has glands that secrete an adhesive material that clumps the food into balls, and microhairs move the food packages toward the mouth. The optimal size for food should be less than 50 – 60 microns. Growing Adults – When feeding larger fish and invertebrates where small food is not needed, adult artemia may be preferred over nauplii. But why should you bother growing adults you ask? I will just feed more newly hatched brine shrimp to make up the difference you say… Well, adult artemia are 20 times longer and 500 times heavier than nauplii and therefore provide more of a meal. There is a myth floating around that adult artemia are not as good for your fish as newly hatched. There is a tiny bit of truth to this, but it depends on what you are feeding. So what’s in it for your fish: Newly hatched artemia are high in fats, about 23% of dry weight. By mid juvenile stage, the fat levels have decreased to about 16 %, and by the time they are pre-adults the fat levels have decreased to about 7%. But, at the same time, the protein content has risen to replace the fat, from about 45% in a newly hatched artemia to about 63% in an adult. Based on this, you should determine what is best for your tank, young fish larvae require a high fat intake for growth and health, while older juveniles and adults need protein for health and reproduction. Also, nauplii are known to be deficient in several essential amino acids, while the adult artemia are rich in all essential amino acids. Adult artemia therefore supply more biomass than nauplii and are more nutritionally complete.
A side note to all this is that rearing microworms for your newborns is also an easy task. A cornmeal or oatmeal culture is all that is needed and the worms live and thrive right in that culture. My belief is that newly hatched artemia is a slightly better nutritional source but that is up for debate. Artemia shrimp can also be raised to adulthood for feeding to large fish whereas microworms stay micro.
The best approach to growing adults is to pick up a 10 or 20 gallon glass aquarium cheap someplace. Take a thin acrylic sheet or Formica, and jam it in the tank, essentially making an oval tank. (This is important to remove the previously mentioned dead spots and improve circulation) Glue all the seams with silicone (3M – Blue tube). Circulation can be enhanced by gluing a partition down the middle of the tank making a raceway arrangement. Best yields are obtained with a good food circulation, animal distribution, and strong aeration. This next step is the hardest to explain without pictures. You need to make six or eight (depending on the length of your tank) air lift tubes. These are simply 1 inch thin wall PVC, cut at 45 degrees on the bottom, with a 90 degree elbow on top. The water level should reach the middle of the elbow, with the tube touching the bottom of the tank, 45 degree cut down. Drill a hole in the 90 degree fitting so you can feed an airline 3/4 of the way down the tube. Glue these tubes to the center divide so that the 90 degree elbows all face in the same direction at a 45 degree angle to the divider. Your creating a mechanism to make a constant flow of water in a clockwise or counter clockwise direction (I don’t think it matters which).
Here is where I should bring up the subject of aeration, avoid the temptation to put in wood airstones to increase flow and aeration. Yes they make beautifully fine bubbles and you can get excellent upflow with them. But it’s these same fine bubbles that will wreak havoc with your artemia. Artemia cannot tolerate fine bubbles since they can lodge in the swimming appendages and kill the little buggers. Artemia can actually ingest fine air bubbles which will wipe them out (I don’t think you can use Gas-X for brine shrimp).
I haven’t had much problem with water quality, so filtration really isn’t necessary on the small scale that were on. Filtration can be included if you feel so inclined, but it will require a screened overflow to a sump or cartridge filter.
Moderate aeration with a coarse or no airstones, good water quality, and generally clean conditions are all important for raising high densities of adult brine shrimp. Since the artemia feed constantly, faster growth rates and better survival is achieved by multiple or continuous feeding over a 24 hour period. Best growth rates are achieved at 25-30 degrees C with salinities of 30-50 ppt and LOW light levels. Remember, artemia are drawn to strong light, so if you install that 175 watt metal halide lamp you had leftover from the reef tank, the little buggers are going to increase their swimming activity and have greater energy expenditure, resulting in slower growth rates. In low light the artemia will spread out in the water column, swimming slowly and achieving more efficient food conservation.
Being a low volume operation, water quality can deteriorate rapidly, especially as biomass increases (I mean, that’s the whole idea right?). The problem usually occurs because of over feeding, which leads to fouling and low oxygen levels. There is a fine line between optimal feeding levels and wiping out our tank, especially when using non-living foods. To help overcome this problem, you need to take care of your artemia tank as much as you pay attention to your aquarium. Here is what you do: Clean the bottom every couple of days. You do this by turning off the air, letting the tank settle, and using that handy flashlight again (I find this works best when done at night). By now we know what our little buddies are going to do. Meanwhile siphon the crap off the bottom of the tank, remember, these guys are going to molt 15 times before becoming adults. (unless you have three hands, prop the flashlight on something). About 20% water change per week is adequate.
My artemia just crap out and die – several causes, there could be insufficient aeration leading to asphyxiation, or you couldn’t resist and used that damned wooden airstone I told you not to use. Or – they’re starving to death. The health status can be checked by looking at how they’re swimming, shine your flashlight into the tank, and they all should rapidly concentrate at the source, this is good. However, slow dispersed swimming indicates things are going to hell quick. If you have access to a microscope you can examine their digestive track which should be full of food (assuming you’ve been feeding themproperly) If the swimming appendages and mouth region are clean, this is good. If they are covered with food particles, this is bad. This condition could be due to the nature of the food or the physiological condition of the animals. Slow growth – Temperature is too low, pH imbalance, salinity is off, inadequate food or lousy food quality.
Your artemia can be stored for future use in several different ways, adult artemia will survive for several days in the refrigerator. If you refrigerate them, be sure to warm them up and give them one last feeding before you feed your fish. This will restore their nutritional quality, after all, they’ve been starving for the past couple of days. You can also freeze them and ice cube tray works perfect for this. Be sure to freeze them in 7-8ppt saltwater for best results. Freezing is neat because all you have to do is toss an artemia cube into the tank, and you have a nifty time release food supply. You have to be careful not to over feed here, they float to the bottom and decompose quick and you can bomb your tank rather rapidly.
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