Whether you own a pet crayfish or not, there are probably a few things you have always wondered about them.
I have selected some of the most commonly asked questions about crayfish including questions about their behavior, aggression, diet, and everything in between.
General Questions about Crayfish
1. What is the biggest crayfish ever caught?
The Tasmanian giant crayfish is the world’s largest crayfish. According to some records, there were some specimens reaching over 31 inches (more than 80 centimeters) long and attaining weights of up to 13 Lb (about 6 kg).
2. Are crayfish good for aquariums?
Generally, crayfish species are very hardy and easy to care for. They are also good scavengers and will help to clean your aquarium. So, yes, they are good for aquariums.
3. Are crayfish good pets?
There are many crayfish species on the pet trade market. They differ in size, colors, and personality traits.
Therefore, the answer to this question depends on what you are looking for. For example, crayfish are easy to care for and easy to feed. Depending on the species, they live from 2 to 6 years in captivity and, generally, reach from 1 to 6 inches (2.5 – 15 cm) in length. They are relatively cheap to buy.
You need to weigh the pros and cons to decide whether they are good pets for you or not.
From my perspective, they are definitely good pets.
- Are Crayfish good pets for beginners? Pros and Cons
- 10 Questions to Ask When Buying Aquarium Crustaceans
- 7 Most Popular Aquarium Crayfish Species
4. What is the lifespan of a crayfish?
Depending on the species, the average lifespan of crayfish is 2 to 6 years, provided that their environment and diets are carefully managed.
The title on ‘longest-lived crayfish’ goes to the Tasmanian giant, which may live for up to 40 years!
5. How can I tell if my crayfish is happy?
Healthy crayfish are happy crayfish. Happy crayfish are active, inquisitive, and always looking for food. Happy crayfish are also prolific breeders.
6. How do you tell if a crayfish is stressed?
Some of the most common signs of stress in crayfish include lethargy, lack of appetite, loss of color, decreased growth, and molting problems.
7. What’s the difference between crayfish and lobster?
Interestingly, if we place crayfish and lobster side by side, most people will never tell the difference between them.
Technically, if it lives in saltwater, it is a lobster. If it lives in freshwater, it is a crayfish. Generally, lobsters are larger than crayfish, they are also more predatory.
8. Do crayfish feel pain when boiled?
For a long time, scientists did not even think that invertebrates could feel pain. In their studies, they presumed that these animals simply reacted mechanically. In other words, there was no implication that central processing and decision-making are involved in responses.
The studies regarding pain in crustaceans continue because their nervous systems do have their own complexity.
For example, in Switzerland, to eliminate any chances, they elected to legislate for lobsters to be stunned or knocked out prior to boiling them. This way they won’t feel any possible pain.
9. How big do Aquarium crayfish get?
Contrary to popular belief, the size of aquarium crayfish is not directly related to the volume of their dwelling. Large crayfish species will grow large even in small tanks. Therefore, you need to do your research beforehand.
For example, dwarf crayfish species attain a maximum length of 1.5 – 2 inches (4 – 5 cm) long.
10. Why is my crayfish tail curled?
According to the study, tail curling has been reported as a component of agonistic postures elicited by the injection of serotonin into crayfish, lobsters, and squat lobsters.
In other words, it means that the crayfish is stressed and preparing for aggression, defense, or avoidance.
The abdomen of crustaceans, such as crayfish and shrimp, curls as a result of muscle contraction. By squeezing their abdominal muscle, they can dart over several meters per second.
Questions about Keeping and Housing Crayfish
11. How many crayfish can you have in a tank?
Can a crayfish live in a 5-gallon tank? How many crayfish can you have in a 10-gallon tank? How many crayfish can you have in a 20-gallon tank?
To answer these questions, you need to know – how big the species grows, is it aggressive, is it territorial, are there enough places to hide in the tank?
For example, the minimum recommended tank size for dwarf crayfish species (Cambarellus diminutus, Cambarellus puer, Cambarellus texanus, Cambarellus patzcuarensis, and Cambarellus shufeldtii) is a 5-gallon (20-liter) tank.
Ideally, a 10-gallon tank (40 liters) will suit them perfectly and you can easily keep 4-6 crayfish in it.
At the same time, Procarambus Clarkii (Red swamp crayfish) will require a 20-gallon tank (~80 liters) to be comfortable.
12. Do crayfish clean tanks?
Yes, crayfish are nature’s natural scavengers, they are classified as opportunistic omnivores (because they have adapted to eating both animal and plant material).
Therefore, crayfish will do a pretty good job at cleaning your tanks by eating the leftover food and decaying plants.
13. Do crayfish need to come out of water?
In spite of the fact that crayfish are fully aquatic animals, they also have specialized gills which enable them to breathe underwater or breathe normal air.
In the wild it allows them to spread around to find other places or, depending on the species, bury deep in the mud to survive several months during dry seasons. For example, Cherax destructor can bury up to 6.5 ft (2 m) deep!
However, under optimal conditions, if the water is properly aerated and there is enough oxygen in the tank, crayfish do not need to come out of the water.
14. Can 2 crayfish live together?
If the tank is big enough and there are many hiding places, even aggressive crayfish species may live together for some time.
I am saying ‘for some time’ because nobody can guarantee that they will not fight. Males are extremely likely to fight when housed together.
Therefore, it can be risky to house multiple crayfish in the same tank unless we are talking about dwarf crayfish species that are not very aggressive and territorial. In this case, it is absolutely possible to keep even more crayfish together.
15. How deep should crayfish water be?
It should be deep enough to completely submerge your crayfish. Remember, they need water to breathe properly.
Important: I would still recommend keeping crayfish and aquarium or paludarium setups.
16. Can crayfish escape a tank?
Easily. All crayfish species are great escape artists. So, a tight-fitting lid is essential for the tank.
17. Do crayfish like warm or cold water?
Generally, crayfish are very resistant to environmental stress, including extreme temperatures (low or hot).
Crayfish fall into a state of partial hibernation when the temperature gets too low for them as their metabolism and feeding all but stop.
In my studies I found that:
|Popular crayfish species||Optimal temperature||Tolerated temperature|
|Cambarellus diminutus||72 – 82 °F (22 – 28 °C)||59 – 86 °F (15 – 30 °C)|
|Brazos Dwarf Crayfish||65 – 75 °F (18 – 24 °C)||40 – 90 °F (4 – 32 °C)|
|Cherax destructor||77 – 82 °F (25 – 28 °C)||33 – 95 °F (1 – 35 °C)|
|Blue crayfish||68 – 75 °F (18 – 24 °C)||No data|
|Procarambus Clarkii||71– 80 °F (22 – 27 °C)||46 – 91 °F (8 – 33 °C)|
|Marbled crayfish||64 – 77 °F (18 – 25 °C)||59 – 86 °F (15 – 30 °C)|
|Dwarf Mexican crayfish||65 – 75 °F (18 – 24 °C)||59 – 87 °F (15 – 31 °C)|
|Cambarellus shufeldtii||68 – 75 °F (20 – 24 °C)||64 – 79 °F (18 – 26 °C)|
|Cambarellus pure||68 – 75 °F (20 – 24 °C)||59 – 86 °F (15 – 30 °C)|
|Cambarellus texanus||65 – 75 °F (18 – 24 °C)||40 – 90 °F (4 – 32 °C)|
|Red claw crayfish||73 – 82 °F (23 – 28 °C)||50 – 95 °F (10 – 35 °C)|
18. Can crayfish live in tap water?
Yes, most crayfish species are pretty tolerant of poor water quality and can live even in tap water.
Important: The tank should be cycled anyway.
However, it is highly recommended that the water in the tank should be free from chlorine and any other harsh chemicals that can be found in most residential tap water.
So, let the water age for a few days. Distilled water can be used, or a chemical water conditioner can be added to eliminate these contaminants.
19. Why do crayfish die?
There can be many reasons which can cause your crayfish’s death. For example, they can die because of bad water parameters, old age, lack of nutrition, excessive aggression from tank mates, copper, or failed molting.
In most cases, all these causes are interlinked with each other. For example, lack of nutrition may result in that crayfish will not store enough calcium in the gastroliths (calcium stones) as a result it may lead to failed molting.
20. How do you know if a crayfish is dying?
You need to look for the signs of stress in crayfish like lethargy, strange behavior, lack of appetite, loss of color, decreased growth, and molting problems.
21. How long can crayfish be out of water?
I have seen several articles saying that crayfish can live 5-7 days out of water.
Well, this is totally not true.
The survivability of crayfish out of water depends exclusively on the humid environment and the species itself.
As long as their gills stay moist, crayfish can survive from a few days to several months. For example, dwarf crayfish species usually die within 48 hours whereas Yabby (Cherax destructors) is able to survive several months in the burrows.
Why is there such a difference?
Because some crayfish species a more adapted to live this way and, basically, go into a state of hibernation.
22. How many babies can a crayfish have?
In crayfish, female fecundity increases with body size. So, large females can have more babies.
|Popular crayfish species||Average clutch size of eggs||Maximum clutch size of eggs|
|Cambarellus diminutus||20 – 40||no data|
|Brazos Dwarf Crayfish||10 – 50||no data|
|Cherax destructor||350 – 450||up to 1000|
|Blue crayfish||50 – 300||no data|
|Procarambus Clarkii||100 – 400||up to 1000|
|Marbled crayfish||~400||up to 700|
|Dwarf Mexican crayfish||20 – 40||up to 60|
|Cambarellus shufeldtii||~ 45||up to 74|
|Cambarellus pure||20 – 40||no data|
|Cambarellus texanus||10 – 50||no data|
|Red claw crayfish||300 – 1000||no data|
|Cherax pulcher||up to 50 eggs||no data|
The females use their appendages to keep the eggs clean from dirt and well oxygenated. Nonetheless, there is high mortality in eggs. In some cases, it can be up to 40%.
According to researchers, increased water uptake in eggs is a significant contributor to egg loss. This is because the increase in egg volume caused by water uptake limits the availability of egg carrying space, resulting in smaller broods.
In addition, young ovigerous females lose a large number of eggs for their lack of care.
23. How can you tell a female crayfish?
Crayfish are sexually dimorphic and their gender can be determined externally by looking at the lower part of their abdomen (the lower part of the white section of the underbelly).
- Males have an extra set of pleopods used for internal fertilization. Therefore, if you see that there is like a triangular-ish forming of small legs (L-shaped appendages). That will indicate a male.
- Females have seminal receptacles and lack the extra pleopods found behind the walking legs on males.
Depending on the crayfish species, there can be other indicators, for example:
- General size.
- Growth rate.
- Size of the claws.
- Colors of the claws.
24. Can crayfish lay eggs without mating?
Yes, there is one species that can reproduce itself with natural cloning techniques – Marbled crayfish.
These crayfish are all genetically identical and their populations are exclusively composed of females.
Questions about Handling Crayfish
25. Can I play with my pet crayfish?
No, crayfish do not like to be handled. They are not pets you can play with. Do not take them out just because you want to.
26. How to play with crayfish?
There is no way you can play with crayfish. Do not trust any article claiming otherwise.
Crustaceans and not very smart animals and, generally, operate on their instinctual nature. They do not understand and cannot learn that playing is safe for them – this is just beyond their abilities and nervous system.
27. How to Hold Crayfish in Your Hand?
The best and safest way to properly hold crayfish is to hold it with your thumb and forefinger just behind its claws to avoid getting pinched.
Note: Pick it only from behind so the claws are facing forward.
28. Can a crayfish hurt you?
Their pinches may hurt a bit but, in most cases, their claws are not sharp and/or strong enough to even break your skin.
29. Do crayfish recognize their owners?
No, they do not. Crayfish are not capable of bonding with their owner. The best you can get from them is that they may recognize you as a low threat. Everything else is just beyond their abilities.
Questions about Compatibility with Fish and other Tankmates
30. What kind of fish can you put with a crayfish?
Actually, this is a very difficult question and the answer depends on many factors including:
- feeding schedule,
- hiding places,
- the personality of crayfish.
For example, let’s take one of the smallest crayfish species like Cambarellus puer. They are probably one of the most social and peaceful crayfish species, but only under several conditions:
- large tank,
- many hiding places,
- well-fed all the time.
But even under these optimal conditions, you can have a crazy crayfish that will attack everything it sees.
With large crayfish species, it gets even more complicated. Therefore, most crayfish are usually better in solitary confinement.
Nonetheless, if you still want to try your luck, you need to follow these rules:
- DO NOT keep them with bottom-dweller fish.
- DO NOT keep them with fish with big and fluffy fins.
- Choose a fast-moving fish.
- Avoid large and aggressive fish that can eat crayfish
31. Can I put crayfish with cichlids?
It is not a good idea to put crayfish with cichlids. Eventually, one will end up hunting the other.
Crayfish are nocturnal animals and prey on smaller aquarium fish while they sleep. However, large and aggressive cichlids will prey on them.
In addition, once the crayfish molts, it can be eaten by cichlids of the same size.
Therefore, I would advise against keeping cichlids with crayfish.
32. Will crayfish kill my fish?
Generally, it depends on the size of your fish. In the wild, crayfish can catch smaller fish while they sleep.
33. Will Crayfish eat guppies?
The great thing about guppies is that they breed faster than crayfish can eat them.
|Popular crayfish species||Potential aggression against guppies|
|Cambarellus diminutus||Very low|
|Brazos Dwarf Crayfish||Very low|
|Cherax destructor||Very high|
|Dwarf Mexican crayfish||Low|
|Red claw crayfish||High|
34. Will Crayfish eat neon tetras?
See the table “Potential aggression against guppies” (Question # 29). The answer is the same. Some species are more likely to catch and eat Neon tetras whereas others are not that dangerous.
35. Can you put crayfish with Oscars?
No, you cannot. Crayfish are part of Oscar’s natural diet in the wild. They cannot be kept in the same tank.
36. Can bettas live with crayfish?
No, it is not advisable to keep any kind of crayfish with bettas.
Even dwarf crayfish, that do not have the capability to kill most fish, will not hesitate to take chunks of betta’s long fins if they feel threatened.
37. Will Crayfish eat shrimp?
The short answer is yes. I would never risk putting crayfish with expensive shrimp.
Although shrimp are pretty fast movers with a quick reaction, there is always the chance they can be caught by a crayfish, especially when shrimp are molting.
Even dwarf crayfish will regularly snap at shrimp when they come too close. Because of that many shrimp in crayfish tanks lose their antennae. The accumulation of such small harassment causes stress to the shrimp.
38. Can snails live with crayfish?
There should not be many problems with the large snails and dwarf crayfish. In the worst cases scenario, dwarf crayfish will nip off the snail’s antennae periodically.
Large crayfish and snails are not compatible in the tank. Generally, they are active predators of snails. For example, in Africa, Procambarus clarkii has been introduced as a biological control agent to reduce snail populations, which are intermediate hosts of schistosomiasis.
Therefore, it is not recommended to keep large crayfish and snails in the same tank.
39. Can frogs live with crayfish?
Generally, no. Frogs and crayfish cannot coexist peacefully in the same tank.
For example, African Dwarf Frogs have very sensitive porous skin, so even dwarf crayfish can easily damage it. There is a very high chance that it will lead to bacterial infections which are often deadly for frogs. As for the large crayfish species, they will eat the dwarf frog.
African Clawed Frogs are completely the opposite. They are aggressive and very persistent predators with a huge appetite. They are omnivorous and can easily swallow small crayfish.
Large crayfish can react (attack) defensively and even cut off some limbs of the African Clawed Frog. At the same time, African Clawed Frogs are strong enough to pull off the legs and claws of the crayfish. Eventually, there will be only one.
40. Can crabs live with crayfish?
Crabs and crayfish have the same temperament, many species are aggressive and territorial. Therefore, they are not recommended to keep together.
41. What are good tankmates for crayfish?
As I have already said in question # 26, this is a very difficult question and the answer depends on many factors including:
- feeding schedule,
- hiding places,
- the personality of crayfish.
If you have dwarf crayfish species, it is possible to keep them with small and peaceful fish like Guppies, Neons, Mollies, Endlers, Dwarf swordtails, etc. If you agree to lose one or two dwarf shrimp here and there you are good to try as well. Medium to large snails are relatively safe too.
As for the large and aggressive crayfish species. In this regard, it is recommended to keep them separately in a species only tank.
Questions about molting and behavior of Crayfish
42. Do crayfish get lonely?
No, Crayfish are generally solitary creatures. They are not social animals.
According to the studies, they can establish some dominance relationship for a short period of time, but this is not enough to call them socials.
43. Are male or female crayfish more aggressive?
On average, male crayfish are more aggressive and territorial in the presence of other males. Females are less aggressive than males but they are still aggressive.
44. Do crayfish die after molting?
No, they do not. Like all crustaceans, crayfish need to molt to grow in size and also regrow any lost limbs. During their life, they can molt dozens of times.
Molting is one of the phases in a molting cycle that includes:
- pre-molt phase,
2. Molt phase,
3. post-molt phase,
4. inter-molt phase.
45. Why does a crayfish die on its back?
When crayfish molt they lay on their back. So, if the molting fails, they stay this way.
46. Can I help my crayfish molt?
You can help them molt if you create optimal conditions for them that include: stable water parameters, feeding, and a comfortable environment.
- Water parameters. Do your research. Every species has its own preferences. On my blog, you can find lots of guides.
- Feeding. It is very important to vary their diet to stimulate their digestive systems and make sure your crayfish get all the nutrients they need.
- Environment. It will be less stressful for the crayfish if there are many places to hide/ Ideally, there are should not be any tank mates that can harm or bother crayfish.
However, if something went wrong during molting, there is nothing that can be done to help crayfish in these cases.
Sometimes people decide to step in and help crayfish to molt. Frankly saying, I have never heard that this kind of “assistance” ended well. So, crayfish have better chances of survival without your help.
47. Why is my crayfish losing color?
Loss of color is one of the earliest signs that the pre-molt stage has begun.
That is because of the detachment of the epidermis from the cuticle (separation of new shell and old one sometimes can be better seen where the joints meet). When it happens the color of the crayfish becomes dimmer or muddy.
Loss of color (fade in color) is also a sign of the stressed crayfish.
48. Why do crayfish hide after molting?
During the early post-molting stage crayfish need to hide because they are too soft to protect themselves and thus may be more vulnerable to bacteria, viruses, or predators.
This is by far the most dangerous stage for the crayfish in their life.
49. How many times do crayfish molt?
Depending on the species, age, temperature, and feeding diet, molt intervals for crayfish range from 1 to 30 days.
For example, baby crayfish molt every few days, while juvenile crayfish may molt every 7 – 10 days. Adult crayfish molt every few months. Fully grown crayfish usually molt only to restore lost limbs.
As an example, Procambarus clarkii needs about 3 months to reach maturity. During this period they molt at least 11 times.
Questions about Feeding Crayfish
50. Do you need to feed crayfish?
Crayfish are omnivorous, scavengers, and will consume any organic food source available to them. However, in an aquarium, because of their size, I would definitely recommend supplementing their diets with vegetables and commercial foods.
Without that, they will starve, become more aggressive, and be susceptible to diseases.
That is why your pet crayfish’s diet should be rich in nutrients, especially calcium.
51. How often should I feed my crayfish?
Adult pet crayfish should be fed every day or two to prevent them from starving and picking on tankmates.
Young crayfish require more frequent feeding; we should feed them every day. They need a lot of food to grow and molt.
52. Do crayfish like carrots?
Yes, crayfish love vegetables like cabbage, lettuce, spinach, carrot, etc.
53. Can Crayfish eat fruit?
Yes, crayfish will eat fruits but you need to be careful with this.
Important: In the aquarium, I would avoid all citrus fruits, tomatoes, avocado, etc. These fruits contain a lot of sugar and can cause a bacterial bloom in your tank. As a result, it can also lead to depletion of oxygen and/or even lower pH in your tank. Another problem is that most of the fruits are too messy.
54. Can Crayfish eat bones?
Crayfish can eat cuttlefish bones. Actually, it is recommended as one of the sources of calcium for them.
As for the real bones, the answer is no. Their jawfoot and claws are not strong enough to crush and eat it.
55. Should I let my Crayfish eat dead fish or old shells?
Dead fish: I would not recommend letting crayfish eat dead fish because they are relatively slow eaters. So, why is that important?
This is because when a fish dies, the process of decomposition takes over, which may foul the water in the tank risking the health of other animals in the tank.
Therefore, a dead fish should be removed from the tank straight away after you have found it.
Old shell: Do not remove the old exoskeleton of the crayfish from your aquarium.
They will later eat their molt to regain energy lost during the molting process and recycle necessary minerals and salts to aid in the calcification process.
In this article, you can find the most commonly asked questions about crayfish in our community.
If you did not find the question you were looking for, feel free to contact me and I’ll do my best to help you.