Triops Care Fact Sheet
by Chip Hannum (updates by Stuart Halliday).
This document was largely put together from extrapolating information in scientific journals regarding triops biology and rearing them in laboratory settings. Other parts are taken from my own experiences or those of other triops owners. To the best of my knowledge, the information is up to date and accurate. I've tried to be complete and thorough, covering all the necessary bases. Still, I can't make any promises as to what your results will be putting any of this info into practice.
These instructions are for both species available commercially, Triops cancriformis and Triops longicaudatus Their requirements in captivity are close enough to be the same for all intents and purposes.
Where differences are known, I've specifically mentioned it. There is one major difference between them you need to keep in mind: T. cancriformis grows slowly compared to T. longicaudatus. In a little over a week T. longicaudatus are usually a few centimeters long; in that same period of time, T. cancriformis will be lucky to be 5 millimeters long.
What kind of container can I use?
Any clean glass or plastic container that is designed to hold food or liquids and let in light can do. It is important that the container not have any soap residue, as it is toxic to triops. Fish tanks are the most flexible, but you can use an old pickle jar as well!
You may want to take a look at our containers page that people have used!
Triops are primarily benthic dwellers, that is, they spend most their time rooting through the debris on the bottom of the pool/container looking for goodies rather than swimming about in open water. The length and width dimensions of the container are far more important than depth. As an example, if you're looking at a choice between a 70 litre (17 UK gallons, 20 US gallons) long versus high aquarium, go with the long.
What size container do I need?
The container should be at least four litre (one gallon) in size if at all possible. Each adult triops needs between two to four liters of water for optimal population density. If you cannot provide them with a larger container, don't worry too much. The triops will be smaller than they might be otherwise, and the number of eggs laid per individual will be reduced, but they will still be healthy.
In spite of their reputation, triops rarely harm other triops of similar size when other food is available. Studies of population density effects have been done on both Triops longicaudatus and T. granarius and the triops got along fine until old age took them regardless of population density. These studies also suggest that, within reason, high density does not directly affect survivability, that the same percentage in any given population will survive a given length of time.
However, anecdotal evidence from triops owners suggests that resource competition does lead to a die off over the first 2-3 weeks to a "comfortable" population density. It is often hard to determine whether effects seen in scientific studies are representative of the general situation or a result of the artificial constraints imposed by the study. In this case, my gut says the owners are right. I, myself, have witnessed a sharp die off of the smaller individuals as the larger members of the population reach breeding size - this may be nature's way of not taking resources away from those most contributing to the next generation.
What kind of water can I use?
For hatching, distilled (often called deionised) water is the safest. There is no chance of the chemical or mineral content of the water affecting hatching and it is the least likely to promote bacterial spikes, which are a leading cause of death with hatchlings. Afterwards, spring, distilled, or tap water treated with a water conditioner that removes Chlorine are all fine.
Other water conditioners may work with tap water as well but AmQuel is the only one that has been used in any of the laboratory studies read. If you try another brand of water conditioner, be certain it removes chlorine, chloramines, and ammonia.
What pH water should I use?
Triops are pH sensitive although the specifics vary from species to species. Some triops are only found in highly alkaline waters while others live in peat bogs. Triops longicaudatus can be killed by pH below 6.0, but tolerates pH up to 10.0. Based upon laboratory studies and conditions they are found in the wild, the optimal pH range for T. cancriformis and longicaudatus is 7.0 to 9.0.
Water pH can be adjusted with chemicals used for aquariums without known problems. Baking soda (sodium bicarbonate) is one commonly available chemical that can be safely used to raise pH. It should not be necessary to lower pH with triops unless you have health issues with your water supply. Triops are fairly resistant to pH changes within their preferred range; in nature, the pH of the small pools they live in may fluctuate within + 2.0 during a given day/night cycle.
Should I use some sort of substrate?
Triops will live and grow in an empty container. You can, however, use any sort of substrate that is safe with freshwater fish. Soil will simulate the natural sediment that occurs in the pools they inhabit most closely, but sand or gravel work equally well (without the huge amount of silt in the water from their incessant digging).
Putting some kind of substrate in the tank will allow for a greater recovery of viable eggs since many of them will be buried where the triops can't make snacks of them. It also allows them to engage in their natural behavior of digging through the bottom of the pool looking for food. As with any aquarium application, wash all gravel and sand thoroughly with plain tap water before using it.
Coral sand available from any Aquarium shop is a good substrate to use, its small particles allow the triops to dig but stops the water getting cloudy if you were to use normal sand. It also raises the pH to around 7.5 which is ideal for triops.
But I heard I had to use soil in the water?
Not necessarily. Larval triops are free swimming filter feeders. They feed on microscopic algae, protozoans, suspended organic particles, etc. Scientists noticed that juvenile triops survived better when they were hatched out with soil from the pond the eggs were collected versus being hatched out in an empty container from isolated eggs.
In addition to the triops eggs, such soil contains organic debris and the cysts of algae, diatoms, and protozoans (cysts hatch out upon wetting much like triops eggs). Native soil also probably helps to buffer the pH to a more triops friendly level. Commercial packets of eggs come with dried pond detritus that contains similar material. Homemade dried gravel or sand with eggs will contain the same as well.
The correlation of larval survival with soil led to a generally repeated instruction from some sources that you should use soil in the water, or at least water that had been mixed with soil first. Enough studies have been done subsequently without soil and no difference in survivability once past the juvenile stage was seen. When care is taken to provide the larvae with a properly conditioned environment and some sort of food infusion, survival is not impacted.
One study, after hatching, raised triops in empty containers of distilled water with only aeration and food. There was no filtration, no water changes, and additional water was only added at the very end of the study when it became necessary to keep the containers from drying completely by evaporation. In these less than optimal conditions, many triops lived nearly 50 days.
So triops are very hardly animals.
Can I use decorations?
If it's safe for freshwater aquaria, you can probably use it with triops.
Putting decorations in the tank won't necessarily do anything for the triops, but it can make the tank more interesting to you.
Note: Some natural decorations might cause changes to the water that wouldn't bother fish but may affect triops, use caution. It appears the addition of red lava stone to my tank caused chemical changes to the water that made moulting much more difficult. Out of a group of 9, 8 died from moulting complications within two weeks of adding some decorative lava stone. If you can't bear risking your triops' lives don't add anything that might leach chemicals or minerals.
How about plants?
Definitely, plants will add to the oxygen levels, break down triops wastes, make the
tank look more interesting, etc. They also make a keen 24-hour salad bar. Triops will eat
anything organic that they can fit in their mouths and aquarium plants are no exception.
On the one hand, this is a good thing because you can provide them with a source of food they can eat any time they are hungry with no danger of the negative effects from overfeeding. On the other hand, stick to something like the £1 ($0.99) bunch of elodea versus a £5.00 ($15) Amazon Sword plant.
Note: since it is generally necessary to break down the triops container between generations you will need to have some way of keeping the plants during this period.
What else can I raise with my triops?
Keeping in mind that triops will potentially eat any of these, you can also raise fairy shrimp and daphnia with your triops. These two species also produce desiccant resistant eggs and hatch out under the same conditions as triops. Fairy shrimp can grow large enough that triops won't eat them if there's enough easier to catch food available. Daphnia, unfortunately, are too bite sized to resist and eventually are wiped in most cases. Another candidate for tankmates are aquatic snails. Although not generally natural cohabitants of triops, they do well together and the snails can help to control algae in the container.
The Golden Apple Snail - Pomacea
(pomacea) bridgesii shown here is particularly recommended as it is interesting,
doesn't eat your plants, doesn't reproduce very fast and is easy to get.
Note: like plants, permanent aquatic residents such as snails will need their own accommodations while the triops container is being dried between generations.
Can I use a filter?
Yes. The safest filter is an undergravel filter. To avoid the possibility of pulling hatchlings into the substrate and killing them, it is best you don't use an undergravel filter until all the hatchlings reach at least a few millimeters in size. After they reach this size, the filter can be used with no problems. An undergravel filter works best with gravel that can't fall down between the slots in the plate, but it can be used with lesser efficacy with sand. It would not work very well with soil, though.
You may also use an internal corner filter. In the case of these types of filters, you must wait until the triops are at least 1 centimeter long or they may be pulled into the filter and killed.
It is possible to use an external filter with larger triops but I don't recommend it except with large tanks. The currents generated by external filters can be very strong, and triops naturally inhabit very still, very quiet pools.
How about a bubbler?
It's a good idea to use a bubbler if you're not using any other sort of filtration. Even if you are using filtration, a bubbler isn't a bad idea during the first days of life when you can't use the filter. Triops are sensitive to oxygen levels, just not in the way you might expect:
It would be very hard to kill triops from lack of oxygen. Oxygen levels must drop well below 1 part per million (ppm) to threaten the life of triops, and even a hot, stagnant desert pool generally contains at least 2 ppm oxygen. Even at very low oxygen levels, triops can survive for extended periods by swimming upside down at the water surface where oxygen levels are highest (they do this looking for food as well, the behavior is not necessarily indicative of low oxygen levels).
However, during the first five or so days of life, triops metabolize at the maximum possible rate based upon oxygen levels, temperature, and available food. Size differences have been demonstrated in multiple lab studies where all conditions were the same except oxygen levels. They even grew faster when available oxygen was increased beyond naturally occurring levels. Secondarily, although adult growth and metabolism is not as sensitive to oxygen levels as the juveniles, fecundity is affected. Therefore, more oxygen equals bigger, faster growing triops and more eggs for the next generation.
What temperature should I keep them at?
For purposes of keeping triops in captivity, the best bet is to make certain that temperatures remain within a range of 22° to 31°C (72° - 86°F). They can survive at lower temps (down to 15°C), but survivability, growth, and fecundity are all impacted. Similarly, they can survive at higher temps, but juvenile survivability is impacted at 32°C and above, and exceeding 34°C can kill adults.
Both species are found in all manner of environmental conditions. There are populations of T. cancriformis in Israel that regularly endure water temperatures in excess of 35°C during the hottest part of the day. Similarly, in spite of the emphasis in many of the available instructions about how T. longicaudatus is a desert dweller and requires warm temperatures, many of the populations studied in the wild are in waters that don't go above 25°C by day and may drop to 16°C at night. However, the general consensus is that T. longicaudatus is the more thermophillic of the two, and most accounts of rearing T. cancriformis are at temperatures well below 30°C. Just something to keep in mind.
Important: Assuming you keep your home at 22°C (72°F) or above, there is no reason you actually need to use artificial heating of any sort in spite of the claims of many triops kit instructions (or any of my suggestions).
A few studies with T. longicaudatus suggest a need for diurnal temperature fluctuations for maximal growth and longevity. In one study, although the average temperature was the same, triops undergoing diurnal temperature fluctuations grew nine times faster initially than the triops kept at a constant temperature. Similar studies have not been done with T. cancriformis, but an analogous requirement is possible.
This can be simulated by using a fish tank heater on a timer, 10-12 hours on, 12-14 hours off. Set the heater such that it is aiming for a temp above actual room temperature and comes on in the early morning and goes off in the evening. This way, the heater kicks on in the morning and the water warms up to the target temperature by late morning/early afternoon - just like what happens when the sun comes up with a natural pool. Then it holds the high temperature through the day and gradually cools off through the night until the heater comes back on again - just like what happens when the sun goes down with a natural pool.
There is a direct relationship between environmental temperature, growth rate, and size. Very similar to the relationship with oxygen described above, triops maximize their metabolism relative to the average temperature they're kept (at least initially). As little as 2°C difference in rearing temperature, all other conditions being equal, results in a definite size differential. Warmer average temps mean faster growing, bigger triops. They also probably make for shorter lived triops - they grow faster but burn out sooner. The relationship is still not fully defined, and this is provided merely as something to consider. However, at least with T. longicaudatus, the consensus of various studies suggests that an average temperature of 25°C (77°F) is the best balance between growth rate, fecundity, and survivability. As a another issue to consider, there is some evidence with T. longicaudatus that after they reach adulthood they grow faster around 20°C versus warmer temperatures. All in all, the exact effects of temperature on size and longevity are still not fully understood so do what seems best or most convenient to you.
Hint: If you use a fish tank heater and don't use filtration or a bubbler, keep in mind that the water immediately surrounding the heater may be much warmer than the water next to the thermometer. In this situation, the thermometer may be reading 31°C but water nearest the heater is actually 36°C and lethal to triops. If you are using a heater but no sort of water circulation, don't aim for a temperature higher than about 25°C. That way you are certain not to cook your triops!
What kind of light do I need?
You can use any artificial light so long as the triops are receiving several hours a day. Even the ambient light in a bright room is sufficient if not optimal. I prefer fluorescent aquarium lights because triops are beautifully colored and the light makes them look their best. Don't use direct natural sunlight because it can cause a small container to overheat quickly.
Some people report giving their triops light 24 hours a day, and some of the kit instructions even recommend this for heating the tank. (I hate this recommendation: you can buy a 25 or 50W heater for about half the price of cheap desk lamp) While there have been no studies of photoperiod effect on triops to date, it seems unlikely that this would not have some effect on their physiology. It is known that they do better with a day/night cycle of temperature variation, it would be surprising if they didn't also prefer some sort of light/dark cycle as well for maximal health. It's obviously not lethal, but unless you absolutely must use a light 24 hours a day, I don't recommend it.
OK, I've got all that straight, onto the hatching!
There are three things you need to provide the eggs with in order to get little triops:
1. Fresh water with a low amount of dissolved minerals.
While adult triops are tolerant of wide ranges in water quality, the eggs are sensitive to the osmotic potential of the water. If your water is particularly hard, the eggs might not hatch.
This is an adaptation to avoid hatching out in an already established and/or dying pool. Right after the pool fills, the water has very little dissolved mineral and organic material content. This indicates that it is a new pool and there are no predators about. After mineral and organic content reaches a certain threshold, no eggs will hatch because this indicates that there may be established predators and/or the pool will not last much longer. If in doubt, use distilled water. You should also perform a major water change (75% or more) prior to adding eggs to an established aquarium to avoid such osmotic inhibition.
On the other hand, keep in mind that pure distilled water will kill triops (and just about anything else aquatic for that matter) as there will be nothing for the newborn to eat. The purpose of the detritus that comes with eggs is to provide a properly conditioned environment of the right amounts of minerals and dissolved organics for the larvae to eat. It is possible if a tank is significantly larger than four or so litres, it may not be sufficient and the water (see below for my suggestion) will actually kill the newly hatched larvae.
The eggs require more than just water to hatch, they also require light. The presence of light indicates that the egg isn't still buried in sediment; it wouldn't do the larval triops any good to go to all the trouble of hatching only to be buried in 7 cm of sediment. After hatching, the free swimming larval triops use the light shining on the pool to find the water surface where they are more likely to find warm temperatures, high oxygen levels, and the sort of food they need.
3. Proper temperature.
Although both T. cancriformis and longicaudatus eggs will hatch over a wide range of temperatures (roughly from 15° - 30°C), both species' optimum hatching rate occurs over a rather narrow range of 22° - 24°C (71 ° - 75°° F). In fact, although I have seen anecdotal reports of warmer temperatures being better for hatching, in laboratory studies, warmer temperatures actually decreased hatching rates by a significant amount. The closer environmental indicators are to showing an ideal habitat, the more eggs that hatch. Fortunately, as it so happens, the optimal hatching temperature for both species is just about room temperature.
One method for hatching that can minimize potential problems is to use small containers, such as as pint or quart jars, for hatching the eggs. Add enough of the egg mixture to lightly cover the bottom of the container and fill to a depth of several centimeters with distilled water.
You can find Distilled or De-Ionised water on sale in most supermarkets, car parts shops or D-I-Y stores. It usually costs less than £1.00 (US$2.00) per litre.
After the eggs hatch I usually add some aquarium plant cuttings as well. You should also go ahead and set up the larger container you will be using at the same time so the water will begin to age - you don't want to be transferring 0.5 cm juveniles to 20 liters of pure distilled water.
The potential advantages of this method are many.
- You are able to use distilled water for hatching without going to the expense of filling an aquarium with several gallons of distilled water. (You can make something like 100 litres of AmQuel treated tap water for the cost of a couple of litres of distilled water).
- The smaller volume of water means that it will achieve "instant pond" status from the debris in the egg mixture much faster.
- A related issue is the size of the container relative to the hatchlings. Young hatchlings are more likely to find what food there is when they only have to search through several hundred milliliters of water versus fifteen thousand. Consider that a commercially available packet of eggs has been portioned to only yield three to twelve triops on average. This number of hatchlings will comfortably get along in a couple of juice glasses until they're several days old.
- The smaller container makes it easier to see and find the new hatchlings. This can be a particularly good thing for first timers who aren't quite sure what they're looking for. The other bonus of the small container is that capturing hatchlings becomes much easier when this is necessary. Egg mixtures may often yield not only triops but fairy shrimp, clam shrimp, and daphnia. If you don't want to take the chance that these will wind up triops snacks, you will want to move them to their own container.
- The combination of not needing to condition a large amount of water and maximizing hatchling survival can allow you to get several triops without using all of your egg supply.
- At the other end of the spectrum, this can let you practice triops "birth control". Completely drying and subsequently hatching all the gravel in a 10-gallon aquarium that's had several triops living in it is going to result in several dozen if not hundreds of hatchlings, of which only 10 - 20 will actually survive to live full life spans. By only drying and hatching a portion of the gravel you won't need to be quite so Darwinian.
- The aquarium plants provide oxygen without the disturbance of a bubbler and generally provide a good source of food in the form of algae and protozoans that will be on the plant when you add it.
Survivability of juveniles is high in these small, controlled conditions and after they get to 0.5 cm or so they can be transferred to a larger container where they will thrive. The caution of this method is that small acts can result in huge changes in such a small environment: overfeeding will result in lethal bacterial spikes and water changes with distilled can be lethal unless you take care to observe the same rule as with an established tank of not changing more than 20%-25% at a time.
How long after I add the eggs will they hatch?
T. longicaudatus eggs generally hatch within 48 hours of hydration. T. cancriformis generally hatch within 48 - 96 hours of hydration. If you are certain there are no larval triops by this time, something is probably wrong. The eggs generally will not hatch after these intervals because the late starters will never catch up in size before they become snacks to the larger triops, another neat adaptation. It's also possible that eggs have hatched, but the larvae died soon after.
Causes for the eggs not hatching or larvae not surviving likely fall into one of two categories. The first is the water is too hard, its osmotic pressure is very high. In this case the eggs will not hatch. Fortunately, eggs that don't hatch on the first hydration will often hatch on subsequent hydrations. The second cause is the water is too soft, pure water will promote a high rate of egg hatching but will actually kill the larvae. Secondarily, if there's not enough algae and other food present for the hatchlings to find, they may not survive. When in doubt, use a smaller container for hatching.
Fortunately, most sellers of triops eggs guarantee them to hatch and will replace them for a nominal fee (usually around $1). If you definitely fail, try again and start with distilled water and a small container as your base.
On the other hand, if you're new at this and aren't quite sure what you're looking for, don't give up immediately. Larval triops are tiny, less than 0.5 millimeters at hatching. Wait a few days before throwing in the towel. In just days, if they're in there, they'll go from those less than 0.5 mm dots to tiny triops 0.5 cm long.
Lastly, with triops, it's never necessarily too late. While eggs usually either hatch on time or not at all, I've had eggs take in excess of a week to hatch for unknown reasons. If you think you've failed but aren't doing anything else with the container, it won't hurt to leave it set up just in case.
Alright! There's little ones swimming, what do I do?
For the first 1-3 days, do nothing other than keep them on a regular light cycle. Then, if you're using heating, you can raise the temperature from hatching temperatures to warmer temperatures conducive to growth and begin a day/night temperature cycle. You may also begin feeding very small amounts of powdered food.
Suitable foods until they reach a size of several millimeters are: dried yeast, food specially formulated for juvenile triops, crushed fish food, crushed adult triops food, food for marine invertebrate filter feeders, algal cultures, etc.
Remember, though, they are tiny, they don't need to eat that much. Although triops consume up to 40% of their body mass in food every day, 40% of the mass of a larval triops is still a very small amount. Overfeeding can lead to high bacteria levels, which can lead to sharp pH shifts and lowered oxygen levels - this can lead to dead triops, be careful with your enthusiasm!
What do I feed them as they get older?
There are a number of triops specific foods sold by people who sell eggs, but you are by no means limited to that. They can and will eat any organic matter in the pool with them that they can fit in their mouths. The number one food for feeding triops in the lab is Tetra-min fish flakes. Basically, any fish food, flake or pellet, floating or sinking, will make a good staple for feeding triops. They are not fussy!
Additionally, you can also feed them tubifex worms, daphnia, brine shrimp, the fruit fly that just landed on your desk, bits of romaine lettuce, mosquito larvae, small bits of dried dog/cat food, and so on. They don't need to eat live food, so don't feel you have to throw little screaming daphnia to the triops (but it is fun). Fresh vegetables pieces make a good food source that doesn't decay quickly or promote bacteria growth - just be sure to wash them thoroughly and/or peel off the outside layer if there's any chance of pesticides. Plants in their tank provide for veggie snacks anytime they're hungry and there's nothing more convenient around.
See our Recipe page for idea on what to feed your Triops!
Triops need to be fed at least twice a day and preferably more often, particularly as they get larger. You'll have to gauge exactly how much to feed based upon how often you can feed them and how much uneaten food is left after a few hours. You don't want uneaten food accumulating and rotting in the tank, but you don't want starving triops either. It's been my experience they do a good job of letting you know when they're hungry, so don't worry too much and pay attention.
Do I need to change the water?
Triops can be pretty filthy critters. If you're not using some sort of filtration, then you should perform at least one 25% water change weekly if not more often. This will help to keep your triops visible as well as cut down on the level of nitrogenous wastes in the water, which can alter pH dangerously and make respiration less efficient. Fortunately, triops are fairly resistant to changes in temperature and pH, so it's not necessary to worry as much as with fish when making sudden changes to their water. Use a siphon tube or other method to remove about one-fourth of the water from their container and then add fresh water. It's as simple as it sounds.
If the water is turning green, you are getting Algae growth. See below on how to remove it.
Depending upon the size of the container and the degree of natural biological filtration, it may be more or less necessary to perform water changes. A 5 gallon tank with 5 cm or more of substrate and some plants is going to remain much cleaner and clearer naturally than a 1 gallon goldfish bowl with no substrate.
With filtration, it is less necessary to perform water changes because the water is kept clean by the filtration and biological action will break down nitrogenous wastes. Triops just don't live long enough for it to become an absolute necessity in the case of a filtered tank. Still, triops water tends to become discolored over time and a weekly 25% water change will avoid this.
Unlike with water changes for a fish aquarium, don't use this as an opportunity to clean the substrate, that's where any eggs will be. What you can do, though, is gently stir up the top of the substrate and after a minute or so siphon water from the middle of the tank. This will remove some silt and sediment without removing the eggs which will sink back to the bottom.
Can I use algicide to kill the algae so I can see them better?
No. Algicide won't kill the triops but has been shown to both stunt their growth and reduce fecundity. If algae is an issue either scrape it off and/or try adding some aquatic snails.
Great Merciful Crap!!! It jumped right out of it's skin
Being arthropods, triops need to shed their exoskeleton in order to grow. They do this multiple times a day when they're young and less frequently as they age. After about two weeks they moult about every one or two days. Watching a triops moult is an amazing thing. They begin with a series of "situps" to stretch the old skin and loosen it up, then they swim into the open water, pop the carapace, and in a matter of seconds leap out of the old skin leaving it perfectly intact other than their exit point.
I mention this in the care section for two reasons. First, jumping out of your skin is not an easy thing to do. If complications occur, a triops can die while trying to moult. They become literally trapped in the older skin. Unable to move their legs enough to adequately breathe, they become weakened and stressed and eventually die. It's unusual, but it does happen. Even when it goes right, the triops will swim around looking as though it just experienced a very rough night for 15 minutes or so afterwards while it stretches the new skin and gets its bearings. Although it looks quite dire, this is normal behavior. Triops are, however, very susceptible to injury while their skin is soft and might be attacked by another triops, snail or simply suffer a fatal injury during this vulnerable period.
The second point is much less serious. The shed skins are largely resistant to breaking down and unless your triops are starving the skins will pile up in the aquarium unless you remove them. Leaving them in, though, is totally harmless; it's merely an aesthetics issue.
Update: If you find your Triops are not shedding their skin completely then this is probably due to a lack of Iodine in the water. Iodine is present in most unprocessed plants food you may be feeding your Triops, so there is usually no need to add supplements.
However if you find your Triops are only part shedding, then we suggest that you find some Kelp tablets from a health food shop and put one tablet in for every 30 Litres once a week or every time you change the water. If you are near the sea you could of course put a small piece of thoroughly washed seaweed in the tank as this sea plant has lots of natural Iodine in it.
|Periodically, triops must shed their skin
order to grow. They leave behind a nearly intact copy of themselves.
It can provide an opportunity to study some of their anatomical features without harassing a living individual or waiting for one to die.
Will my triops breed?
Very probably. Most populations of T. cancriformis are bisexual but female biased and can reproduce parthenogenetically. All of the reproductive forms are known within T. longicaudatus. If you only have one triops, it can probably produce viable eggs. If you have two or more, you're probably set no matter what their reproductive pattern.
If you have a female or hermaphrodite you can see the brood pouches (egg sacs) on the legs near the end of the carapace. Triops will generally begin laying eggs at about two weeks or so in age and produce a brood of eggs approximately every day.
You can see the pinkish colored eggs as they gather in the brood pouches. The number of eggs produced varies widely based upon specific sub-population characteristics, but is somewhere in the neighborhood of 15 - 60 eggs per brood. The larger the female/hermaphrodite, the more eggs produced per brood and the more rapidly broods are produced. They may attach the eggs to objects in the tank or simply lay them in the substrate. Keep in mind that very few of these eggs will hatch without drying first, and even if some do hatch, as long as adults are around, the hatchlings will become snacks.
How big will they get?
The exact size that your triops will grow to is largely dependent upon the size of their container and population density. The largest triops of any species that I know of was a T. cancriformis specimen caught in the wild by Erich Eder, it measured 11 cm (~4.5 in) in overall length. That, however, was a unusually large specimen. In general, expect that triops raised in captivity will get between 4-8 cm in overall length.
How long will they live?
Triops evolved to survive in naturally temporary pools. As inhabitants of such, there has never been any pressure for them become long-lived creatures. Their strategy is one of "get in and get out". In the lab, T. longicaudatus has a maximum lifespan of about 50 days and T. cancriformis a maximum lifespan of about 65 days.
These maximum lifespans in the lab agree with data from field observations on triops survival. The average lifespan for both species is around 30 - 40 days with some individuals beginning to die off as soon as 2 weeks after hatching. Secondarily, some may suffer premature deaths from moulting complications or other reasons. There are occasional reports of "Methuselah" triops that live much more than 2 months, but don't count on it for your guys. That's the bad news. The good news is you can usually do it all over again without much trouble.
How do I do that, start over?
The bare bones method (and most common) is to turn off any filters, heaters, etc. and siphon the water down to the substrate. Alternatively, you could leave the tank going and scoop out some of the substrate into another container. If you're not using any sort of substrate, siphon off as much water as you feel comfortable without sucking up the eggs at the bottom. At room temperature, let the substrate or container dry completely and leave it dry for at least 2 weeks.
Alternatively if you gently heat the damp substrate by placing it near a radiator until the substrate looks dry then check to see if the substrate can be easily moved about in its container when you tilt it. If so then it's probably dry enough.
You can store dried eggs and substrate for years (ten years is not unheard off), but you only need to wait 2 weeks for good hatching rates. Letting it go longer than 2 weeks will not change the hatching rate measurably and there is no reason to wait several months as some instructions say.
What you can do is optionally freeze the substrate containing the eggs for a few days at this point in a air tight container. This simulates the passing of an entire season and has been shown in lab studies to increase the percentage of eggs that hatch on the first hydration.
That's it. Set up your container and add fresh water to start the whole process over again. If you're adding water to several centimeters of substrate, either pour the substrate into the water gradually, or stir it up after you add the water. This will free the eggs and let them temporarily float to the surface where they will get light and initiate the hatching response.
For my personal method and recipe for preparing eggs/hatching detritus click here.
If you have a sachet or two of that silicon gel used to keep suitcase interiors dry then put it in with the eggs in a air and light tight container and put them in a cold fridge for several days. Just keep the eggs and substrate dry and away from the light. This simulates an egg drying out and being buried in mud in the wild.
Can you give me an idea what all this costs?
At the cheap end of the spectrum, a £3.00 (US$6.00) 3 litre food container, a £2.00 (US$4.00) bottle of AmQuel or SafeGuard, and £2.00 (US$2.50) in fish food will probably suffice for successfully raising triops. Toss in £4.00-6.00 (US$5.00 - $8.00) for the initial purchase of Triops eggs, and you've got a hobby for under £15 (US$30.00). If you recycle an old jar and someone gives you some eggs, it's going to be more like £6.00 (US$10). Although what I've outlined above are idealized conditions, these guys didn't survive 200 million years by being overly picky!
At the nicer end of the spectrum, you can buy a 5 or 10 gallon aquarium, glass versa top, incandescent strip light, heater, undergravel filter, air pump, gravel, accessories, and triops eggs for between $50 - $75 total. Going with a fluorescent light will add around $20 - $25 to the cost.
So, depending on how fancy you want to get, raising triops will cost you between $15 - $100. The choice is totally dependent on what you want. Your triops will be happy with anything that lets them swim, eat, and lay eggs.