OscarWilde
Fishaholic
V2.1 Updated: 01/11/2011
Common Names: Australian red claw crayfish, Redclaw crayfish, Blue lobster, Blue crayfish, Blue yabby, Electric blue lobster, Electric blue crayfish, North Queensland Yabby, Queensland Redclaw, Cherax Quad.
Scientific Name: Cherax quadricarinatus
Scientific classification:
Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Crustacea
Class: Malacostraca
Order: Decapoda
Suborder: Pleocyemata
Infraorder: Astacidea
Superfamily: Parastacoidea
Family: Parastacidae
Genus: Cherax
Species: C. quadricarinatus
Origin: Australia, also found in Papua New Guinea.
Max size: Approximately 8”
Lifespan: Four to five years.
Care/Housing: They can be kept at a range of temperatures from room temperature (18 degrees C though to the high 20's) however 24-25 degrees is considered optimum. The water needs to be clean, well-aerated, free of pollution and hard and alkaline.
Cherax quadricarinatus are best kept in a 20 USG/90 litre, well-filtered species tank containing plenty of rocks\caves for shelter with good water movement and aeration.. They do not require any access to land so the tank can be filled.
They will also DESTROY any live plants you have in the tank so do not add to your planted tank! One of mine has recently cut up a plastic plant! They also have a reputation as escape artists and are will certainly try to climb up objects such as heaters and filters so this should be considered when aquascaping. If your C. quadricarinatus is trying to escape regularly then this may be a sign that the environment is low in Oxygen and he/she is looking for a better place to live.
Tankmates: Opinion is strongly divided on the matter of tank mates. I myself keep C. quadricarinatus in each of my of my community tanks one of which has a Sailfin Plec and am yet to lose a single fish or see any damage. Others report their specimens killing and eating all of the fish in their tanks so it would probably be best to expect to lose at least a few fish if you choose to add to a community tank. It should also be noted that C. quadricarinatus will be an easy meal for a large fish such as an Oscar.
Feeding: C. quadricarinatus will eat just about anything but it is important to remember that the majority of their diet is be vegetable. There are specialist foods available but mine have done well on a combination of catfish pellets, any flake food that will sink to the bottom, the odd plant, peas courgette, cucumber, carrots and Bloodworm\fish occasionally as treats.
Sexing and breeding Redclaw Crayfish: - Thanks to boboboy for this section
Redclaw mature at between 7 and 12 months. the most obvious sign of this is the development of a red patch on the outside of the anvil section of the claw of a male. this patch is soft, but i would not suggest you try to find out if i am telling the truth! Females tend to develop their blue colour at this time, so the development of deep blue claw tips is the most noticeable sign.
Sexing:
The sex organs of these Cray are placed in the leg area. the male will have two holes as the base of the first pair of legs, looking from the tail forwards. the females have them on the third pair of legs, looking from the tail. During mating the male leaves a packet of sperm, just on or below the first set of legs. when the female spawns she drags the eggs form her own organs and pulls them through the sperm packet, hopefully fertilizing them as she does.
Breeding:
Redclaw can and do breed throughout the year, however, in nature, the season is between September and April. Often this is just a drop in the number of berries, between May and August. incidentally a berrie, is the term used to describe the clutch of eggs a cray carries.
The real factors in breeding these guys are, light, temperature and water quality. with the exception of these stats, the time of year has nothing to do with breeding.
Ideal conditions seem to be:
- 14 hours of light, not too bright, cray dont like bright light. -
- Clean high O2 water
- A temperature of between 80 and 84f.
If we assume that you give the cray 12 hours of light, this is the recommended daily quota and keep your cray at 78F. It is suggested that you slowly reduce the light to 10 hours per day and reduce the temperature to 72-74F. This being achieved you should start to raise the temp and increase the light, sadly you will need to experiment with the time you take to do this, but doing it over three days should suffice. Increase the light to 14 hours per day and the temp to 84f.
The female will carry the "berrie" for six to ten weeks before hatching, the young then spend a couple of weeks still attached to the female. as they come free, it is best to remove the young, as they will soon become food for their mother if you do not.
Redclaw cray do not have a larval stage, they emerge as fully formed adolescents. this is not true of all crayfish. some go through Instars, a developmental stage all arthropods go through. Its just in the Redclaw these stages occur whilst the infant is still in the egg.
Comments: Cherax quadricarinatus I have seen in stores including the ones I have purchased have has some degree of damage to their antenna. I would guess that this occurs during transport or from battles due to being kept at close quarters with other specimens while waiting to be sold. Both of mine healed completely after their first moult in my tanks.
Identification and Legal Information for the UK: This is the only freshwater crayfish that you can legally keep if you live in the UK. The legislation is in place because the native species of crayfish, Austropotamobius pallipes, has suffered following the introduction of Red signal crayfishes that escaped from farms introducing a deadly disease into the wild. There is an article on identification here.
Further Information:
If your Crayfish Does Escape!
If your Cray does escape, your first action, whilst looking for the Cray, should be to put a container of tank water in a dark corner of every room the cray can get to dehydration is what kills the Cray, and it is a hard road to recovery. Just put about 1 inch of water in the container, this gives the Cray some water to sit in as its on its wanders. Leave a lid by it, it come in handy later!
When you do find your Cray, place it in one of the tank water containers you have placed about, top it up so the water comes half way up the flanks of the Cray, then pop on the lid, but leave a corner open, or punch holes in the top.
Now place the Cray in a cool place (remember cool mean something different to Cherax quadricarinatus than most Cray), and cover with a damp cloth. The cool temperature and the dark will slow the metabolism of the Cray, allowing it to re-hydrate whilst minimising the harm caused by the injury. Keep a check on the Cray, though too much checking will slow or damage the recovery.
Over time (it is hard to say how long), the Cray will start to be more active, eventually causing quite a row. When this happens, empty the water and replace it with tank water of the correct temperature, you may need to do this slowly, especially with cool water cray that have had a real temperature drop.
After a few hours you can think of putting the critter back in its tank. As you do this put it in upside down, legs up, this will avoid any air being trapped under the carapace, then rotate it right way up and drop it.
If all has gone well you should start feeding the next day. Sadly this experience will not make the Cray any more likely to stay in its tank, which leads me to think they are of a similar intelligence to MP's, always making the same mistakes and never learning!
Images:
Male Cherax quadricarinatus
How to hold out of tank.
Female Cherax quadricarinatus
Moult split
Moult empty
Cherax quadricarinatus and friends!.
Sources:
FF: especially posts from boboboy
PFK
Wikipedia
Department of Fisheries, Western Australia
Posted 02 March 2008 - 01:36 AM
V2.0 Updated: 18/03/2008
Common Names: Australian red claw crayfish, Redclaw crayfish, Blue lobster, Blue crayfish, Blue yabby, Electric blue lobster, Electric blue crayfish, North Queensland Yabby, Queensland Redclaw, Cherax Quad.
Scientific Name: Cherax quadricarinatus
Scientific classification:
Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Crustacea
Class: Malacostraca
Order: Decapoda
Suborder: Pleocyemata
Infraorder: Astacidea
Superfamily: Parastacoidea
Family: Parastacidae
Genus: Cherax
Species: C. quadricarinatus
Origin: Australia, also found in Papua New Guinea.
Max size: Approximately 8”
Lifespan: Four to five years.
Care/Housing: They can be kept at a range of temperatures from room temperature (18 degrees C though to the high 20's) however 24-25 degrees is considered optimum. The water needs to be clean, well-aerated, free of pollution and hard and alkaline.
Cherax quadricarinatus are best kept in a 20 USG/90 litre, well-filtered species tank containing plenty of rocks\caves for shelter with good water movement and aeration.. They do not require any access to land so the tank can be filled.
They will also DESTROY any live plants you have in the tank so do not add to your planted tank! One of mine has recently cut up a plastic plant! They also have a reputation as escape artists and are will certainly try to climb up objects such as heaters and filters so this should be considered when aquascaping. If your C. quadricarinatus is trying to escape regularly then this may be a sign that the environment is low in Oxygen and he/she is looking for a better place to live.
Tankmates: Opinion is strongly divided on the matter of tank mates. I myself keep C. quadricarinatus in each of my of my community tanks one of which has a Sailfin Plec and am yet to lose a single fish or see any damage. Others report their specimens killing and eating all of the fish in their tanks so it would probably be best to expect to lose at least a few fish if you choose to add to a community tank. It should also be noted that C. quadricarinatus will be an easy meal for a large fish such as an Oscar.
Feeding: C. quadricarinatus will eat just about anything but it is important to remember that the majority of their diet is be vegetable. There are specialist foods available but mine have done well on a combination of catfish pellets, any flake food that will sink to the bottom, the odd plant, peas courgette, cucumber, carrots and Bloodworm\fish occasionally as treats.
Sexing and breeding Redclaw Crayfish: - Thanks to boboboy for this section
Redclaw mature at between 7 and 12 months. the most obvious sign of this is the development of a red patch on the outside of the anvil section of the claw of a male. this patch is soft, but i would not suggest you try to find out if i am telling the truth! Females tend to develop their blue colour at this time, so the development of deep blue claw tips is the most noticeable sign.
Sexing:
The sex organs of these Cray are placed in the leg area. the male will have two holes as the base of the first pair of legs, looking from the tail forwards. the females have them on the third pair of legs, looking from the tail. During mating the male leaves a packet of sperm, just on or below the first set of legs. when the female spawns she drags the eggs form her own organs and pulls them through the sperm packet, hopefully fertilizing them as she does.
Breeding:
Redclaw can and do breed throughout the year, however, in nature, the season is between September and April. Often this is just a drop in the number of berries, between May and August. incidentally a berrie, is the term used to describe the clutch of eggs a cray carries.
The real factors in breeding these guys are, light, temperature and water quality. with the exception of these stats, the time of year has nothing to do with breeding.
Ideal conditions seem to be:
- 14 hours of light, not too bright, cray dont like bright light. -
- Clean high O2 water
- A temperature of between 80 and 84f.
If we assume that you give the cray 12 hours of light, this is the recommended daily quota and keep your cray at 78F. It is suggested that you slowly reduce the light to 10 hours per day and reduce the temperature to 72-74F. This being achieved you should start to raise the temp and increase the light, sadly you will need to experiment with the time you take to do this, but doing it over three days should suffice. Increase the light to 14 hours per day and the temp to 84f.
The female will carry the "berrie" for six to ten weeks before hatching, the young then spend a couple of weeks still attached to the female. as they come free, it is best to remove the young, as they will soon become food for their mother if you do not.
Redclaw cray do not have a larval stage, they emerge as fully formed adolescents. this is not true of all crayfish. some go through Instars, a developmental stage all arthropods go through. Its just in the Redclaw these stages occur whilst the infant is still in the egg.
Comments: Cherax quadricarinatus I have seen in stores including the ones I have purchased have has some degree of damage to their antenna. I would guess that this occurs during transport or from battles due to being kept at close quarters with other specimens while waiting to be sold. Both of mine healed completely after their first moult in my tanks.
Identification and Legal Information for the UK: This is the only freshwater crayfish that you can legally keep if you live in the UK. The legislation is in place because the native species of crayfish, Austropotamobius pallipes, has suffered following the introduction of Red signal crayfishes that escaped from farms introducing a deadly disease into the wild. There is an article on identification here.
Further Information:
If your Crayfish Does Escape!
If your Cray does escape, your first action, whilst looking for the Cray, should be to put a container of tank water in a dark corner of every room the cray can get to dehydration is what kills the Cray, and it is a hard road to recovery. Just put about 1 inch of water in the container, this gives the Cray some water to sit in as its on its wanders. Leave a lid by it, it come in handy later!
When you do find your Cray, place it in one of the tank water containers you have placed about, top it up so the water comes half way up the flanks of the Cray, then pop on the lid, but leave a corner open, or punch holes in the top.
Now place the Cray in a cool place (remember cool mean something different to Cherax quadricarinatus than most Cray), and cover with a damp cloth. The cool temperature and the dark will slow the metabolism of the Cray, allowing it to re-hydrate whilst minimising the harm caused by the injury. Keep a check on the Cray, though too much checking will slow or damage the recovery.
Over time (it is hard to say how long), the Cray will start to be more active, eventually causing quite a row. When this happens, empty the water and replace it with tank water of the correct temperature, you may need to do this slowly, especially with cool water cray that have had a real temperature drop.
After a few hours you can think of putting the critter back in its tank. As you do this put it in upside down, legs up, this will avoid any air being trapped under the carapace, then rotate it right way up and drop it.
If all has gone well you should start feeding the next day. Sadly this experience will not make the Cray any more likely to stay in its tank, which leads me to think they are of a similar intelligence to MP's, always making the same mistakes and never learning!
Sources:
FF: especially posts from Raptorrex
PFK
Wikipedia
Department of Fisheries, Western Australia
Common Names: Australian red claw crayfish, Redclaw crayfish, Blue lobster, Blue crayfish, Blue yabby, Electric blue lobster, Electric blue crayfish, North Queensland Yabby, Queensland Redclaw, Cherax Quad.
Scientific Name: Cherax quadricarinatus
Scientific classification:
Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Crustacea
Class: Malacostraca
Order: Decapoda
Suborder: Pleocyemata
Infraorder: Astacidea
Superfamily: Parastacoidea
Family: Parastacidae
Genus: Cherax
Species: C. quadricarinatus
Origin: Australia, also found in Papua New Guinea.
Max size: Approximately 8”
Lifespan: Four to five years.
Care/Housing: They can be kept at a range of temperatures from room temperature (18 degrees C though to the high 20's) however 24-25 degrees is considered optimum. The water needs to be clean, well-aerated, free of pollution and hard and alkaline.
Cherax quadricarinatus are best kept in a 20 USG/90 litre, well-filtered species tank containing plenty of rocks\caves for shelter with good water movement and aeration.. They do not require any access to land so the tank can be filled.
They will also DESTROY any live plants you have in the tank so do not add to your planted tank! One of mine has recently cut up a plastic plant! They also have a reputation as escape artists and are will certainly try to climb up objects such as heaters and filters so this should be considered when aquascaping. If your C. quadricarinatus is trying to escape regularly then this may be a sign that the environment is low in Oxygen and he/she is looking for a better place to live.
Tankmates: Opinion is strongly divided on the matter of tank mates. I myself keep C. quadricarinatus in each of my of my community tanks one of which has a Sailfin Plec and am yet to lose a single fish or see any damage. Others report their specimens killing and eating all of the fish in their tanks so it would probably be best to expect to lose at least a few fish if you choose to add to a community tank. It should also be noted that C. quadricarinatus will be an easy meal for a large fish such as an Oscar.
Feeding: C. quadricarinatus will eat just about anything but it is important to remember that the majority of their diet is be vegetable. There are specialist foods available but mine have done well on a combination of catfish pellets, any flake food that will sink to the bottom, the odd plant, peas courgette, cucumber, carrots and Bloodworm\fish occasionally as treats.
Sexing and breeding Redclaw Crayfish: - Thanks to boboboy for this section
Redclaw mature at between 7 and 12 months. the most obvious sign of this is the development of a red patch on the outside of the anvil section of the claw of a male. this patch is soft, but i would not suggest you try to find out if i am telling the truth! Females tend to develop their blue colour at this time, so the development of deep blue claw tips is the most noticeable sign.
Sexing:
The sex organs of these Cray are placed in the leg area. the male will have two holes as the base of the first pair of legs, looking from the tail forwards. the females have them on the third pair of legs, looking from the tail. During mating the male leaves a packet of sperm, just on or below the first set of legs. when the female spawns she drags the eggs form her own organs and pulls them through the sperm packet, hopefully fertilizing them as she does.
Breeding:
Redclaw can and do breed throughout the year, however, in nature, the season is between September and April. Often this is just a drop in the number of berries, between May and August. incidentally a berrie, is the term used to describe the clutch of eggs a cray carries.
The real factors in breeding these guys are, light, temperature and water quality. with the exception of these stats, the time of year has nothing to do with breeding.
Ideal conditions seem to be:
- 14 hours of light, not too bright, cray dont like bright light. -
- Clean high O2 water
- A temperature of between 80 and 84f.
If we assume that you give the cray 12 hours of light, this is the recommended daily quota and keep your cray at 78F. It is suggested that you slowly reduce the light to 10 hours per day and reduce the temperature to 72-74F. This being achieved you should start to raise the temp and increase the light, sadly you will need to experiment with the time you take to do this, but doing it over three days should suffice. Increase the light to 14 hours per day and the temp to 84f.
The female will carry the "berrie" for six to ten weeks before hatching, the young then spend a couple of weeks still attached to the female. as they come free, it is best to remove the young, as they will soon become food for their mother if you do not.
Redclaw cray do not have a larval stage, they emerge as fully formed adolescents. this is not true of all crayfish. some go through Instars, a developmental stage all arthropods go through. Its just in the Redclaw these stages occur whilst the infant is still in the egg.
Comments: Cherax quadricarinatus I have seen in stores including the ones I have purchased have has some degree of damage to their antenna. I would guess that this occurs during transport or from battles due to being kept at close quarters with other specimens while waiting to be sold. Both of mine healed completely after their first moult in my tanks.
Identification and Legal Information for the UK: This is the only freshwater crayfish that you can legally keep if you live in the UK. The legislation is in place because the native species of crayfish, Austropotamobius pallipes, has suffered following the introduction of Red signal crayfishes that escaped from farms introducing a deadly disease into the wild. There is an article on identification here.
Further Information:
If your Crayfish Does Escape!
If your Cray does escape, your first action, whilst looking for the Cray, should be to put a container of tank water in a dark corner of every room the cray can get to dehydration is what kills the Cray, and it is a hard road to recovery. Just put about 1 inch of water in the container, this gives the Cray some water to sit in as its on its wanders. Leave a lid by it, it come in handy later!
When you do find your Cray, place it in one of the tank water containers you have placed about, top it up so the water comes half way up the flanks of the Cray, then pop on the lid, but leave a corner open, or punch holes in the top.
Now place the Cray in a cool place (remember cool mean something different to Cherax quadricarinatus than most Cray), and cover with a damp cloth. The cool temperature and the dark will slow the metabolism of the Cray, allowing it to re-hydrate whilst minimising the harm caused by the injury. Keep a check on the Cray, though too much checking will slow or damage the recovery.
Over time (it is hard to say how long), the Cray will start to be more active, eventually causing quite a row. When this happens, empty the water and replace it with tank water of the correct temperature, you may need to do this slowly, especially with cool water cray that have had a real temperature drop.
After a few hours you can think of putting the critter back in its tank. As you do this put it in upside down, legs up, this will avoid any air being trapped under the carapace, then rotate it right way up and drop it.
If all has gone well you should start feeding the next day. Sadly this experience will not make the Cray any more likely to stay in its tank, which leads me to think they are of a similar intelligence to MP's, always making the same mistakes and never learning!
Images:
Male Cherax quadricarinatus
How to hold out of tank.
Female Cherax quadricarinatus
Moult split
Moult empty
Cherax quadricarinatus and friends!.
Sources:
FF: especially posts from boboboy
PFK
Wikipedia
Department of Fisheries, Western Australia
Posted 02 March 2008 - 01:36 AM
V2.0 Updated: 18/03/2008
Common Names: Australian red claw crayfish, Redclaw crayfish, Blue lobster, Blue crayfish, Blue yabby, Electric blue lobster, Electric blue crayfish, North Queensland Yabby, Queensland Redclaw, Cherax Quad.
Scientific Name: Cherax quadricarinatus
Scientific classification:
Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Crustacea
Class: Malacostraca
Order: Decapoda
Suborder: Pleocyemata
Infraorder: Astacidea
Superfamily: Parastacoidea
Family: Parastacidae
Genus: Cherax
Species: C. quadricarinatus
Origin: Australia, also found in Papua New Guinea.
Max size: Approximately 8”
Lifespan: Four to five years.
Care/Housing: They can be kept at a range of temperatures from room temperature (18 degrees C though to the high 20's) however 24-25 degrees is considered optimum. The water needs to be clean, well-aerated, free of pollution and hard and alkaline.
Cherax quadricarinatus are best kept in a 20 USG/90 litre, well-filtered species tank containing plenty of rocks\caves for shelter with good water movement and aeration.. They do not require any access to land so the tank can be filled.
They will also DESTROY any live plants you have in the tank so do not add to your planted tank! One of mine has recently cut up a plastic plant! They also have a reputation as escape artists and are will certainly try to climb up objects such as heaters and filters so this should be considered when aquascaping. If your C. quadricarinatus is trying to escape regularly then this may be a sign that the environment is low in Oxygen and he/she is looking for a better place to live.
Tankmates: Opinion is strongly divided on the matter of tank mates. I myself keep C. quadricarinatus in each of my of my community tanks one of which has a Sailfin Plec and am yet to lose a single fish or see any damage. Others report their specimens killing and eating all of the fish in their tanks so it would probably be best to expect to lose at least a few fish if you choose to add to a community tank. It should also be noted that C. quadricarinatus will be an easy meal for a large fish such as an Oscar.
Feeding: C. quadricarinatus will eat just about anything but it is important to remember that the majority of their diet is be vegetable. There are specialist foods available but mine have done well on a combination of catfish pellets, any flake food that will sink to the bottom, the odd plant, peas courgette, cucumber, carrots and Bloodworm\fish occasionally as treats.
Sexing and breeding Redclaw Crayfish: - Thanks to boboboy for this section
Redclaw mature at between 7 and 12 months. the most obvious sign of this is the development of a red patch on the outside of the anvil section of the claw of a male. this patch is soft, but i would not suggest you try to find out if i am telling the truth! Females tend to develop their blue colour at this time, so the development of deep blue claw tips is the most noticeable sign.
Sexing:
The sex organs of these Cray are placed in the leg area. the male will have two holes as the base of the first pair of legs, looking from the tail forwards. the females have them on the third pair of legs, looking from the tail. During mating the male leaves a packet of sperm, just on or below the first set of legs. when the female spawns she drags the eggs form her own organs and pulls them through the sperm packet, hopefully fertilizing them as she does.
Breeding:
Redclaw can and do breed throughout the year, however, in nature, the season is between September and April. Often this is just a drop in the number of berries, between May and August. incidentally a berrie, is the term used to describe the clutch of eggs a cray carries.
The real factors in breeding these guys are, light, temperature and water quality. with the exception of these stats, the time of year has nothing to do with breeding.
Ideal conditions seem to be:
- 14 hours of light, not too bright, cray dont like bright light. -
- Clean high O2 water
- A temperature of between 80 and 84f.
If we assume that you give the cray 12 hours of light, this is the recommended daily quota and keep your cray at 78F. It is suggested that you slowly reduce the light to 10 hours per day and reduce the temperature to 72-74F. This being achieved you should start to raise the temp and increase the light, sadly you will need to experiment with the time you take to do this, but doing it over three days should suffice. Increase the light to 14 hours per day and the temp to 84f.
The female will carry the "berrie" for six to ten weeks before hatching, the young then spend a couple of weeks still attached to the female. as they come free, it is best to remove the young, as they will soon become food for their mother if you do not.
Redclaw cray do not have a larval stage, they emerge as fully formed adolescents. this is not true of all crayfish. some go through Instars, a developmental stage all arthropods go through. Its just in the Redclaw these stages occur whilst the infant is still in the egg.
Comments: Cherax quadricarinatus I have seen in stores including the ones I have purchased have has some degree of damage to their antenna. I would guess that this occurs during transport or from battles due to being kept at close quarters with other specimens while waiting to be sold. Both of mine healed completely after their first moult in my tanks.
Identification and Legal Information for the UK: This is the only freshwater crayfish that you can legally keep if you live in the UK. The legislation is in place because the native species of crayfish, Austropotamobius pallipes, has suffered following the introduction of Red signal crayfishes that escaped from farms introducing a deadly disease into the wild. There is an article on identification here.
Further Information:
If your Crayfish Does Escape!
If your Cray does escape, your first action, whilst looking for the Cray, should be to put a container of tank water in a dark corner of every room the cray can get to dehydration is what kills the Cray, and it is a hard road to recovery. Just put about 1 inch of water in the container, this gives the Cray some water to sit in as its on its wanders. Leave a lid by it, it come in handy later!
When you do find your Cray, place it in one of the tank water containers you have placed about, top it up so the water comes half way up the flanks of the Cray, then pop on the lid, but leave a corner open, or punch holes in the top.
Now place the Cray in a cool place (remember cool mean something different to Cherax quadricarinatus than most Cray), and cover with a damp cloth. The cool temperature and the dark will slow the metabolism of the Cray, allowing it to re-hydrate whilst minimising the harm caused by the injury. Keep a check on the Cray, though too much checking will slow or damage the recovery.
Over time (it is hard to say how long), the Cray will start to be more active, eventually causing quite a row. When this happens, empty the water and replace it with tank water of the correct temperature, you may need to do this slowly, especially with cool water cray that have had a real temperature drop.
After a few hours you can think of putting the critter back in its tank. As you do this put it in upside down, legs up, this will avoid any air being trapped under the carapace, then rotate it right way up and drop it.
If all has gone well you should start feeding the next day. Sadly this experience will not make the Cray any more likely to stay in its tank, which leads me to think they are of a similar intelligence to MP's, always making the same mistakes and never learning!
Sources:
FF: especially posts from Raptorrex
PFK
Wikipedia
Department of Fisheries, Western Australia
