Dwarf Mexican Crayfish

Dwarf Mexican Crayfish  – Detailed Guide: Care, Diet, and Breeding

by Michael

Having an aquarium with Dwarf Mexican crayfish (Cambarellus patzcuarensis) is no easy task. There are plenty of rules to be followed and preparations to be made in order to keep your crayfish happy and healthy. That is why knowing all you can about your little critters will help you keep them thriving. Therefore, as usual, I combined different results of scientific studies and experience of aquarists in this guide to provide all information about Dwarf Mexican crayfish.

Dwarf Mexican crayfish is a robust, tolerant and relatively easy to breed. They will not drastically limit your options as their bigger cousins do. In some cases, they can be even one of the best candidates for beginners! However, if you are planning to keep Dwarf Mexican crayfish in a community tank with fish or shrimp the risk of aggression remains.

I would like to start off by saying that the term Dwarf Mexican crayfish refers to several different species called the Cambarellus. Coming from the Cambaridae family they are one of the few types of crayfish that can be kept in captivity relatively safely. Other types of crayfish are known to the wildlife community as killers and diggers. They got their nicknames from the way they kill other fish, dig at the bottom of the tank, and completely destroy any plants in the tank. 

Quick Notes about Dwarf Mexican Crayfish

Name Dwarf Mexican Crayfish
Common Names Mexican Crayfish, Orange Crayfish
Scientific Name Cambarellus patzcuarensis var orange
Tank size (optimal) 10 gallons (~40 liters)
Keeping Easy-medium
Breeding Easy-medium.
Size up to 4 – 5 cm (~ 2 inches)
Optimal Temperature 18 – 24°C  (~65°F – 75°F)
Optimal PH 7.5 – 8.0 (6.5 – 9.0)
Optimal GH 3 – 18 
Optimal KH 3 – 15
Optimal TDS 200 – 300 (100 – 500)
Nitrate Less than 20 ppm
Diet Detritivore / omnivore
Temperament Conditionally Peaceful
Life span up to 2 years
Color Form Orange, brown, rust, marbled.

Dwarf Mexican Crayfish and other Dwarf Species of Crayfish

According to the study, despite the fact that 17 currently recognized taxa have been described in, or assigned to, the genus Cambarellinae, little analysis of the genus exists. They all look very similar, they are all small (about 4-5 cm or 2 inches) and can be called dwarf crayfish.

Nowadays, on the market, we can find many varieties of dwarf crayfish, which classification based on the color. For example,

1. Cambarellus ninae – brown-colored,
2. Cambarellus montezumae – yellow-colored,
3. Cambarellus patzcuarensis  – orange-colored, 
4. Cambarellus shufeldtii – grey/reddish to brown-colored.

However, frankly saying, this method of “classification” is completely unreliable. The point is that these species of dwarf crayfish can crossbreed. As a result, some aquarists believe that Cambarellinae patzcuarensis is not a pure line anymore. It is a hybrid version of C. montezumae and C. patzcuarensis (in order to get better/intense coloration). Basically, it means that nobody can be sure what kind of species they might have! 

Dwarf Mexican Crayfish Description

size Dwarf Mexican CrayfishDwarf Mexican crawfish comes from Lake Pátzcuaro, a volcanic crater lake in Michoacán which is located in the southwest of the major city of Morelia, Mexico. Wild individuals of this crayfish are mostly tan, brown, and rust color.

However, Dwarf Mexican crawfish are also available in bright colored morphs that are dramatically different from their normal, relatively drab, wild type coloration. The orange color morph of the dwarf species originated in the Netherlands (bred by Juan Carlos Merino in the 1990s).

This color morph also called “CPO – Cambarellus patzcuarensis var orange” is a very attractive and popular strain among hobby keepers. Actually, it completely took over the pet niche for this species. Once again, this mutation comes from the crayfish being bred in captivity and not in the wild. 

Mexican dwarf orange crayfish is suitable for smaller sized tanks (attaining a maximum length of 4-5 cm or 2 inches).

The lifespan of these tiny bright creatures is only about 2 years but have been known to live even a little bit longer.

Facts: Dwarf Mexican crayfish (Cambarellus patzcuarensis) is listed on the IUCN red list of endangered species. 

Dwarf Mexican Crayfish Behavior

In most guides about the Dwarf Mexican crayfish, you will see that they are not aggressive creatures but instead are known for their peaceful nature. Well, compared to many other crayfish, this is true… but only to some degree.

These creatures despite their size are quite territorial in nature and will defend their homes and threaten each other if they come too close to each other. They have claws not for nothing!

Dwarf Mexican crayfish (mostly males) can be especially aggressive towards their own kind. Therefore, if you overpopulate your tank they will “regulate” the number with their own way. In addition, from time to time you will notice that one or two would lose an arm. Of course, it will grow back. However, it shows us their temper.

Another thing that you should remember that these crayfish are excellent escape artists. They have quite strong legs (to get out of the tank) and can spend some time out of the water.

Note: That is why, when keeping any type of Dwarf crayfish, it is a good idea to make sure the water line in your aquarium is not too high. 

Dwarf Mexican Crayfish Male and Female Difference

male and female differenceDwarf Mexican CrayfishThe female and male species can be told apart 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. That will indicate a male.

Females have seminal receptacle and lack the extra pleopods found behind the walking legs on males. Females do not have the same section. There will not be that triangular-ish forming of small legs. What you will see is a small nub. That will indicate a female. 

Note: It is easy to differentiate males and females once they hit about 1/2 an inch (~1.5 cm). At this size, they will be about 2 months old.

Keeping Dwarf Mexican Crayfish 

water parameters Dwarf Mexican CrayfishIf you have a tank with Dwarf Mexican crayfish it is recommended to having no more than two in a 10-gallon tank and no more than 4 in a 20-gallon tank.

Exactly the same as shrimp, Crayfish are extremely sensitive to nitrates and ammonia (you can read more about “Nitrates in Shrimp Tank. How to Lower them” right here). Therefore, if the tank is not cycled do not add the crayfish to cycle the tank. They will not survive.

Make sure you have you PH levels at least 7.5 – 8.0. The point is that Dwarf Mexican crawfish comes from Lake Pátzcuaro. According to the research, high pH and alkalinity, categorize Lake Patrcuaro as an alkaline lake with its inorganic carbon components dominated be carbonates (30%) and bicarbonates (70%). In general, pH values are similar in most locations, but the lowest value (pH = 8.8) was observed in the north basin.

Note: There are many reports that aquarists kept them in the range on 6.0-7.0 as well. Although it is not recommended.

In addition, Dwarf Mexican crayfish prefer to live in the water with high values of TDS.

The temperature of the tank needs to be anywhere from 18 – 24°C (~65°F – 75°F). According to some studies, these crayfish can easily tolerate temperature from 15 – 31C (~59°F – 87°F). For example, they were even found in the pond where the temperature fluctuates from 31 to 37 C (~87°F – 98°F) during the year.

According to another study, where the three temperatures 18° ± 1° C, 22° ± 1° C and 26° ± 1° C were tested. Significant differences were found regarding female survival and viability, but not in the percentage of spawning. Biologists found that the increased viability was recorded at 26° C and the highest survival rate of females was recorded at 18° C.

As we can see, this is a very hardy animal, but regular water changes are vital to its optimal health. Installing the proper filtration system along with changing the water will ensure that your crayfish stays properly oxygenated.

Best Substrate for Dwarf Mexican crayfish

Many decapod groups such as shrimps, crabs, and crayfish live in the bottom of both lotic and lentic areas in inland waters. Therefore, substrate type can play a very important role for them.

During my research, I have found the study “Growth Performance and Substrate Preference of Juvenile Mexican Dwarf Orange Crayfish (Cambarellus patzcuarensis) in Different Substrate Types”. Six different substrates were tested in this study. Total length and weight measurements of Dwarf Mexican crayfish were carried out biweekly during the 100-days experiment.

Substrate for Dwarf Mexican crayfishParticle sizes of other substrates for pebble is 3-5 mm, sand is 800-1000 μm, calcite is 800-1000 μm with white color and basalt is 300-500 μm with greyish black color. Particulates substrates (pebble, sand, basalt, and calcite) covered the bottom of aquaria in the layer of 0.5 cm.

The results of the study: The results of the growth experiment indicate that Mexican dwarf orange crayfish gained significantly higher weight when raised on basalt substrates. Bare glass (control group) was the lowest among the other substrates.

According to the result of substrate preference experiment, crayfish spent more time on basalt substrate when given a choice of substrates. These results pointed out that the type of substrate is an important parameter for growth performance and selection of life habitats on this species.

Substrate and growth of Dwarf Mexican crayfishNote: In nature, Dwarf Mexican crayfish are found in lava sandy areas. So that the basalt is close to the natural substrate of this species with its small particles and greyish black color. 

Filter and Dwarf Mexican crayfish

Due to the small size of the offspring (the offspring of the Dwarf Mexican crayfish are very tiny (about 2 mm)), the filter intake should be covered with a sponge or net. Once again, basically, it is the same procedure as with baby shrimp.

You can read my article “The Best Filtration System for Breeding Shrimp”.

Personally, I believe that that Matten filter will be the best option for the Dwarf Mexican crayfish. A large amount of surface area in those types of filters allows plenty of room for microorganisms to colonize. They will help keep the water clean, and the currents produced by the filter will not endanger the small baby crayfish.

Driftwood, Rocks, Plants and Dwarf Mexican crayfish

Driftwood, rock, and plants are essential parts to a successful shrimp tank. Well, with Dwarf Mexican crayfish they are not essential, they are crucial!

You have to provide lots of hiding places to prevent/reduce stress (during molting) and territorial battles. If the tank has a lot of secluded places, even in crowded tanks, it will be rare for any specimens to lose a pincer. Otherwise, they can seriously harm (or even kill) one another.

You can read my article “Driftwood in Shrimp Tank”.

You can read my article “Top 5 Plants for Your Shrimp Tank”.

Dwarf Mexican Crayfish Molting

The same as a shrimp, Dwarf Mexican crayfish need to shed their exoskeleton in order to grow in size and also regrow any lost limbs. An adult crayfish only needs to shed its skin up to five times a year whereas a juvenile crayfish will shed its exoskeleton every 7 to 10 days.

When the crayfish is in the molting process they will look for a place to hide, either under a shell or in a crack between rocks at the bottom of the tank. The reason they like to stay hidden during this process is that they are completely defenseless until their skeleton fully hardens.

Feeding Dwarf Mexican Crayfish 

Dwarf Mexican crayfish almost always spend their time scavenging for food and wandering around their habitat. They are omnivores and prefer organic food. These species enjoy blackworms, crushed snails, earthworms and brine shrimp. As a special treat, you can feed your Dwarf Mexican crayfish Algae wafers, which is something they seem to really enjoy.

Keep in mind these little critters are also scavengers and will eat basically anything you throw in the tank. You will want to feed your crayfish bottom dwelling live food along with sinking pellets of any brand.

Surprisingly crayfish also enjoy vegetables such as shelled peas and zucchini.  You can read my article “How to Blanch Cucumbers and Zucchini for Shrimp, Snails, and Fish the Right Way.”

Supplement their diet and make sure they get enough calcium (for the exoskeleton) by regularly feeding specialized invert foods.

I highly recommend to read my article “How to Supplement Shrimp and Snails with Calcium”.

Note: Lots of aquarists noticed that snails and any meaty foods are preferred and it helps them grow much faster. Algae wafers, vegetables should only be a supplemental diet. The main diet needs to be meat (protein) anyway.

Tip: Color enhancing food such as Hikari Shrimp CuisineHikari Micro Wafers, and Hikari Tropical Crab Cuisine (link to check the price on Amazon) can be a good option to go for if you want to maintain or improve that bright orange coloration.

You can read my article “How to Enhance Shrimp Color?”

How Often to Feed Dwarf Mexican Crayfish?

There is no easy answer to this question because it has to be a delicate balance with crayfish and teammates (fish or shrimp).

What I want to say is that if you feed too much, you will risk to foul up the water and cause a lot of problems. On the other hand, it is absolutely important crawfish be fed enough not to go after the shrimp or fish and the shrimp need to be fed enough to grow the colony.

Breeding Dwarf Mexican Crayfish.

Mating 

mating Dwarf Mexican CrayfishIf you are one of the many Dwarf Mexican crayfish owners who want to breed their colony, it is not as hard as it would seem. Breeding them is considered such an easy process because not much intervention is needed on the caretakers part. The crayfish will do the work all on their own.

First of all, you need to make sure you have at least one male and one female in your tank. When breeding is initiated, the male flips over and pins down the female and deposits sperm near her sperm receptacle. 

Note: If you wait and watch closely the male crayfish will pounce on top of the female crayfish placing sperm inside of what’s referred to as the female’s sperm receptacle. The female crayfish will then fold over her tail, placing it under her body so that she may fertilize her eggs.

According to the study about the Dwarf Mexican crayfish, a higher percentage of spawning at 18 C occurred with 89%. At 18 C and 22 C, the females spawned on more than one occasion. The spawning rate was lower at 22 C and 26 C (about 66.67%).

Note #2: It is worth mentioning that it was found that the initial size of reproduction and spawning in Dwarf Mexican crayfish (Cambarellus patzcuarensis) was 23 – 25 mm (~1 inch), which coincides with Cambarellus montezumae (another dwarf species). They reach maturity at around 2.5 – 3 months old.

Eggs

female with eggs Dwarf Mexican CrayfishFemale Dwarf Mexican crayfish can usually have anywhere between 20 and 40 eggs. In some cases, big females can carry up to 60 eggs. The female uses her appendages to keep the eggs clean from dirt and well oxygenated. Her body also keeps the eggs protected from predators and other dangers in her habitat.

Keep in mind that the temperature plays a huge role here as well. For example, biologists noticed that females retain on average between 13.92 and 21.69 eggs. The lowest was found at 26 C (79F) and the largest number was presented by females at 18 C (64F). It usually takes from 3 – 4 weeks to hatch depending on temperature.

Regarding the loss of eggs, researchers attributed it to the individual factor (experience). Young ovigerous females lose a large number of eggs for their lack of care, while females with experience in handling of their spawning, under similar conditions, present a lower loss.

In addition, egg loss is proportional to the size of the Dwarf Mexican crayfish, so small females lose more eggs than females larger size.

Hatching Day and Baby Dwarf Mexican Crayfish

baby Dwarf Mexican CrayfishIf you can see dark spots (developing eyes) on the eggs it means that they are about to hatch.

After hatching, they can still cling onto the mother in their curled up position and stay with her for a few days. Until their shells are hard enough for them to swim off on their own they are completely defenseless. Even more, at this stage of life baby Dwarf Mexican crayfish can only wiggling but unable to actually get up and walk. 

Baby Dwarf Mexican crayfish can basically be fed the same thing you feed the adults, it just needs to be in smaller proportions. Sometimes (during first few days) the hatchlings will scavenge for their food at the bottom of the tank along with their mother.

The females usually do not attack their babies in the first few days after hatching. However, this is not a rule. Therefore, ideally, you need to isolate them (for example, in a little plastic container inside the tank to protect them from the adults). Unfortunately, there are many reports about people who keep their babies with adult Dwarf crayfish and get poor success in keeping them alive. 

Important to know about Dwarf crayfish babies

DO NOT keep different generations together. Dwarf crayfish babies are also very aggressive. Especially, larger ones to smaller ones. Even with a small size difference, they will not hesitate to catch smaller ones and kill them. Only babies of similar size can be kept relatively safe together.

At the early stages, you need to feed Dwarf crayfish babies daily. Otherwise, they will die due to hunger or aggression. As long as they are well-fed, they will not attack each other to cannibalize.

Of course, you will see mock fight anyway but they jump away almost immediately.

Tip: If your crayfish eggs have hatched and fall off the mother, scoop them up gently and keep them in a safe place inside the tank. There is a possibility that it will develop.

You can build DIY egg tumbler to increase the chances of survival. Read my article to learn more how to do that “Save the Eggs from a Dead Shrimp”.

Dwarf Mexican Crayfish and Cannibalization

I have already mentioned it before but one of the issues with keeping them is cannibalization. Therefore, DO NOT overestimate how many you can keep or Dwarf Mexican Crayfish will sort that out for you.

Hatchlings and juveniles should be removed into their own containers, as these often got eaten by adults. Once they are about 1.5-2 cm (2/3 inch), you can set them with the adults. It should be relatively safe by then for them to be not seen as free food. 

Dwarf Mexican Crayfish and Fish Tankmates

If you want to keep your crayfish from becoming prey it is recommended that no aggressive fish be kept in the same tank and the habitat be kept as peaceful as possible. You will want to have lots of shells, gravel and other things at the bottom of your tank for the crayfish to hide in. Having a good place for the crayfish to hide is not only important to the molting and breeding process but will make their environment feel more like home.

Aquarists noticed that Dwarf Mexican Crayfish have a tendency to react defensively. They can behave aggressively towards a fish if they feel threatened. They do not have the capability to kill most fish, but they will not hesitate to take chunks of fins if they feel threatened.

In most guides about Dwarf Mexican Crayfish, you will read that they are compatible with anything and everything. However, it is very important to mention that each Dwarf Mexican Crayfish has individual personality meaning that some people have had crayfish successfully in community tanks while others have had disastrous results.

In general, they do not limit your options as their bigger cousins do. Even small fish, snails, and other water plants can be housed with the Dwarf Mexican Crayfish. For example, they can live together with guppies, mollies, boraras, dwarf swordtails, and snails, and even the offspring of these species survive. Only ill and weak specimens are removed by the crayfish, helping to preserve the health of the entire community.

If your tank has a big fish do not expect to see your crayfish during the day. They will spend the daytime hours hiding from danger. Make sure the hiding places are too small for the big fish to access.

Dwarf Mexican Crayfish, Shrimp and Snail Tankmates

Frankly saying, you will get mixed answers on this because it is going to depend on the individual. I have read that people manage to keep Dwarf Mexican Crayfish with Dwarf shrimp and they were doing just fine. 

Personally, I do not think that this is a good idea to keep them together if you are planning to breed your dwarf shrimp. Dwarf Mexican Crayfish can easily overpower shrimp because they are almost twice as big (with few exceptions, like Amano shrimp or Bamboo shrimp). In addition, any molting shrimp is an easy meal for a crayfish. If crayfish gets hold of a shrimp, the shrimp usually does not have any chances.

Of course, we can look at this from another angle. Healthy shrimp are too fast for them. So, if they caught a shrimp I would guess it was ill, slow, genetically weak or simply too stupid. Therefore, it must go anyway. Basically, they will do culling for you.

Read more about “Culling Shrimp. Selective Breeding.”

Even baby Dwarf Mexican Crayfish can try to catch baby shrimp. Therefore, keeping them together with dwarf shrimp should be avoided. Nonetheless, if you agree to lose one or two shrimp here and there you are good to try.

Tip: They will not go after the shrimp if you feed them (at least it will reduce the chances).
Note: Dwarf Mexican Crayfish can eat bladder (pest) snails. Unfortunately, they can also nip off the antennae of larger snails.

Conclusion

Nowadays, keeping an aquarium is a popular hobby worldwide. The interest in crayfish is increasing. Aquarists interest in crayfish species for many causes such as their interesting behaviors, individual personalities, attractive colors, and patterns.

Adding Dwarf Mexican Crayfish to your aquarium is a great idea, only if you are ready to fulfill their needs and provide a certain level of attention and care. They can be very peaceful in a community tank when they are satisfied and contented. In this case, they are shrimp, fish, plants friendly (almost) and compatible with anything and everything.

All in all, Dwarf Mexican Crayfish are extremely amusing and fun to watch.

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