The Pom Pom Crab (Ptychognathus Barbatus) is fully aquatic, freshwater crab (Do not confuse it with the marine species that goes by the same name). These crabs are a true rarity and quite new to the hobby.
Freshwater Pom Pom crabs are very cute, friendly and small creatures. They are one of the least aggressive crab species in the aquarium hobby. All these qualities make them suitable for nano tanks.
Unfortunately, there is not much information about them. I have done extensive research and could not find any official studies regarding this species. I mean that we do not know their biology, ecology, ethology, and reproduction. Besides basic taxonomy, the science has not studied the Pom Pom Crab (Ptychognathus Barbatus) at all. Nonetheless, people already keep them in their tanks.
Basically, the only way to find out more about the freshwater Pom Pom crabs was to ask aquarists who keep or kept them. This is what I have.
Quick Notes about the Pom Pom Crabs
| Name | Freshwater Pom Pom Crabs |
| Common Names | Hong Kong crabs or Cheerleading crabs |
| Scientific Name | Ptychognathus barbatus |
| Tank size (minimal) | 5 gallons (~20 liters) |
| Keeping | Moderate |
| Breeding | Very Difficult |
| Size | 1.5 – 2.5 cm (0.6 – 1 inches) |
| Optimal Temperature | 22 – 28°C (~72°F – 82°F) |
| Optimal PH | 6.8 – 7.2 (6.2 – 7.6) |
| Optimal GH | 6 – 8 |
| Optimal KH | 2 – 6 |
| Optimal TDS | 150 – 200 |
| Nitrate | Less than 20 ppm |
| Diet | Omnivore / Algae eater |
| Temperament | Peaceful (Less aggressive than many other crabs) |
| Life span | up to 1 year |
| Color Form | Yellow-brownish with spots |
Natural Habitat of the Pom Pom Crabs
The species is found in Taiwan, China, Japan, New Caledonia, Indonesia, Philippines, Malaysia, India, Comoros, and Madagascar.
They dwell and thrive near the mouth of a narrow river, hidden among the interspaces of pebbles or rocks in the calm freshwater spring at the depth of 0.2 m.
Description of the Pom Pom Crabs
The freshwater Pom Pom crab (Ptychognathus Barbatus) get their name from the little hair tufts growing from their pinchers.
This is a small-sized crab. Its carapace size is usually between 15 – 25 mm (0.6 – 1 inch). Some aquarists say that when they are full-grown, they may be a little over an inch.
This species is unique among crabs in having a very broad carapace, long and slender legs.
Body and pereopods pale yellow or pale brown (various speckly shades), setae (hair) brown. The body color changes frequently. It often matches the color of the living environment.
Lifespan: no official date. In captivity, according to the reports, they do not live for more than 1 year.
The Behavior of the Pom Pom Crabs
They have some fascinating behavior and personality. The freshwater Pom Pom crabs are extremely active and not timid at all. Unlike Thai Micro Crabs (Limnopilos naiyanetri), which you will never see again, you will often see them running (quite fast) all around the perimeter of their tank.
Males can spar with each other at times. However, they usually do not damage.
Regarding other inhabitants of the aquarium, the freshwater Pom Pom crabs are pretty much completely peaceful. They do not seem to care about anything else in the tank.
Although they are fully aquatic, they can function on land as well. They seem to go around and seek out the tallest place to stand, where they can stay outside of water for a while.
They love to burrow and use their claws to push the sand like a little bulldozer.
Note: The freshwater Pom Pom crabs climb extremely well. This is one of the main reasons why people lose them. Therefore, secure the tank (seal the top completely, lower the water level, hide any cords) or they will crawl out of the aquarium.
Pom Pom Crabs Molting
Like with all crustacean, the freshwater Pom Pom crabs need to molt (shed their old exoskeleton) to grow. After shedding, when the body is still soft and flexible, they start pumping their bodies with water, thus increasing it in size.
Molting is the most important and most dangerous process for them. Without a shell, they are extremely vulnerable. Therefore, to prevent predation, freshwater Pom Pom crabs will dig burrows and molt there. If they disappeared for a day or two, most probably they were molting.
The freshwater Pom Pom crabs need calcium to mineralize (harden) the shell. I highly recommend reading my articles:
Are the Freshwater Pom Pom Crabs Plant Safe?
There are no reports that Pom Pom crabs eat live plants. They will not cut them down as well. These crabs are not as bad as crayfish. So, in this sense, they are plant safe.
However, as I have already mentioned they enjoy digging a lot. Therefore, they might dig up some finer rooted plants from the substrate. As a result, they potentially can destroy plants that get in the way of their general activity.
Note: The best option will be to keep floater plants or tough plants with a solid root system.
Sexing Pom Pom Crabs
Sexing the freshwater Pom Pom crabs is easy but you have to see the underside for that. On the underside of the shell, there is a V-shape section. It has a different shape and size in males and females.
Males also have a fat pair of claws with a tuft of bristles at the “wrist” joint (the Pom Poms), and females do not. Large females can have some tuft but it will be very feeble.
Female claws are distinctly smaller, and much narrower than that of males.
In general, males are slightly bigger than females.
Related article:
Feeding Pom Pom Crabs
The freshwater Pom Pom crabs are an omnivore species so they can eat about anything edible they come across.
Although they lean more towards the herbivore side, occasionally they also need protein-rich frozen foods (such as bloodworms, live brine shrimp, etc).
Pom Pom crabs are great scavengers, they will eat algae and detritus in your tank.
Sometimes people think that because of their tufts they are sort of a filter feeder (as Vampire shrimp or Bamboo shrimp, read my guides about them). Well, in fact, this is not exactly so. They do not intentionally use their “Pom Poms” to filter the water column. Pom Pom crabs simply do not sit, motionless in one place that long. However, they will eat off it anything that stuck there.
In addition, they will also readily accept fish or shrimp pellets, flakes, algae wafers, (for example, Hikari Shrimp Cuisine, Hikari Micro Wafers, and Hikari Tropical Crab Cuisine (links to check the price on Amazon). Once again, do not forget about a calcium supplement.
Note: Many times we can see that other guides and articles warn “Avoid any food product, plant fertilizer, etc. that contains Copper of any form”.
Personally, this is an exaggeration. In my article “How Copper Affects Dwarf Shrimp” I described why shrimp (Actually, it applies to all crustaceans, not just shrimp but to crabs and crayfish as well) need some copper (because it is an essential part of their blood)! The concentration of copper (in food) is too small to hurt.
Keeping Pom Pom Crabs
There seems to be very little information about proper husbandry for this crab. To make it even worse, a lot of reports contradict each other. There is no unanimous opinion among the aquarists, and we do not know their natural water parameters.
However, most of the freshwater Pom Pom crabs keepers say that their care is almost identical to Neocaridina species (Cherry shrimp). Therefore, they will require pH 7.0 – 7.2, GH 6 – 8, KH 2 – 6, TDS 150 – 200, temperature 22 – 28°C (~72°F – 82°F).
Note: Some aquarists manage to keep them at pH 6.4 – 7.2 and believe that this is their optimal number. Unfortunately, nobody knows for sure.
In addition, it is really difficult to say how hardy these crabs are because nobody knows their lifespan in the wild.
Freshwater Pom Pom crabs do not need a large aquarium. A small colony can be sustained in a tank of at least 5 gallons (~20L) as long as it is fully cycled and heated.
Because they are burrowers, they are going to need sand or fine gravel substrate.
Note: These crabs like to burrow underneath stationary objects to hide. Make sure you have enough of those and soft sediment so they have sufficient territory and ground to burrow under.
Do not forget that they need careful acclimation (ream more about it).
Basic Tank Accessories (links to check the price on Amazon)
*Remineralazers for RO/DI water: Salty Shrimp GH/KH+ |
Breeding Pom Pom Crabs
They live in freshwater rivers but their larvae need brackish or saltwater for their development. Unfortunately, nobody knows anything else about their reproduction.
In my research, I could find only mentions that Ptychognathus barbatus larvae have several (at least two) larval stagers and megalopa stage.
The duration of the stages is not known. There is no information about larvae requirements or diet.
So far, we do not have any reports of successful breeding the freshwater Pom Pom crabs (Ptychognathus barbatus) in captivity.
Pom Pom Crabs and Suitable Tankmates
Freshwater Pom Pom crabs are appreciated by fish and shrimp keepers for their peaceful nature and are the perfect addition to a community tank.
They do not display aggression at all except during the occasional short squabble with their own species. They can even be kept with shrimp! For example, some aquarists keep them with Bamboo shrimp, Cherry shrimp, Amano shrimp, etc. without losses.
If you do spot your Pom Pom crabs eating a shrimp or fish then you can safely assume it was already dead. Sure, they may pick fights with fish over food but nothing serious. Shrimp usually do not mess with Pom Pom crabs and prefer to retreat.
When choosing tankmates for your Pom Pom crabs keep in mind that they are not very large and might easily fall prey to hungry tankmates. Go for peaceful fish only and avoid anything that might be able to fit a crab in its mouth.
Note: Potentially, they can attack very small snails.
You can read my article “Сherry Shrimp in a Community Tank. Tips to Make it Successful” and use the same principles for the freshwater Pom Pom crabs
Conclusion
A relatively recent addition to the aquarium hobby, the freshwater Pom Pom crabs are quickly gaining popularity due to their peaceful nature and fun behavior. It makes them a great option if you are looking for tankmates for your shrimp or small fish.
Related articles:
How to Set Up a Freshwater Crab Tank
References:
- A new species of Ptychognathus Stimpson, 1858 (Crustacea: Decapoda: Brachyura: Varunidae) from the Ryukyu Islands, southwestern Japan. Zootaxa. July 2006. DOI: 10.5281/zenodo.173175
- Land, mangrove and freshwater decapod crustaceans of Mayotte region (Crustacea Decapoda). Atoll research bulletin592(592):1-60. January 2013. DOI: 10.5479/si.00775630.592
- On the Post-Larval Stage of Ptychognathus barbatus (A. MILNE-EDWARDS) (Crustacea, Brachyura, Grapsidae). By Kensaku MURAOKA and Susumu SATOH. Kanagawa Pref. Mus. No. 10. August 1977 (written in Japanese language).
Is it okay to keep with a male betta fish in a densely vegetated aquarium?
I do not want to give you false promises.
Betta with Pom Pom crabs – it will always be a risk.
Best regards,
Michael
Also how often do they need to be fed?
Hi Olivia,
If there are enough algae and detritus in your tank you can simply let them scavenge for the leftovers.
If you are not sure, I would recommend feeding Pom Pom crabs at least 2 – 3 times a week.
Best regards,
Michael
Thank you so much for this article!!! I love these guys but had failed utterly in keeping them alive. Now I understand (I think) where I went wrong!
Hi C Smith,
You are welcome:)
Best regards,
Michael
What was it? Looking to hopefully bypass the learning curve.
do they climb? or “jump” I have a 36 gallon tank, and generally leave my water a little low, but i do have air tubing, heater that i wonder if they will use to climb out of the tank. I do not have a secure lid on my tank of anykind!
Hi Daryl,
Pom pom crabs are pretty good at climbing and I mentioned it in the guide.
Be very careful.
Best regards,
Michael
Can you have these in a tank with eco complete as the substrate?
Hi Kristin,
Yes, it is possible to keep Pom Pom crabs in the tank with Eco complete.
Best regards,
Michael
Can i give it cooked veggies such as zucchini or lettuce ?
Hi Jenn,
Yes, you can. Just don’t forget to remove uneaten food.
Best regards,
Michael
Thanks for the great article! Inadvertently I think I’m the first person to breed these in captivity, I have 10+ babies running around.
These crabs are not fully aquatic as everyone thinks, I noticed them coming up onto the moss island I made even before the babies. One stayed there for a long time in the moss and then died, and now all these babies. The babies I can only guess went through their larval stage in the wet moss. They pop in and out of the moss and I’m feeding them shrimp pellets there. They are perfect copies of the adults.
I have a theory that in nature they must go to the river’s edge and lay their eggs in the moss, and the babies develop there safe from predators. Now that mine look like mini adults they are starting to explore the tank. Babies first spotted Dec. 19/2020. I started with 5 adults about 7 months ago. Hope this information helps someone!🙂
Hi Devin Fan,
Thanks for the feedback!
Nonetheless, I will disagree with you here.
As I mentioned in the article – “Although they are fully aquatic, they can function on land as well. They seem to go around and seek out the tallest place to stand, where they can stay outside of water for a while”. However, it does not mean that they require land to survive. This is the main difference.
Best regards,
Michael
Hi Michael,
I had three pom pom crabs for the past three months. I ended up getting 5 cory panda catfish and within 2 weeks all 3 crabs died do you have any idea if they can be tank mates I have tried looking for info not much out there 29 gallon tank with shrimp and some fish my setup. TIA
Hi Jose Moya,
Cory panda are not that big to eat Pom pom crabs. Generally, these are very peaceful fish.
Anyway, did you change anything in the tank? What was the behavior of the crabs? How did they die (was it during molting)?
What is your setup?
Best regards,
Michael
I would love to hear more about how you were able to breed them since there supposedly aren’t any documented cases. Can I chat with you more through email or something?
Would these crab be safe in a 29g tank with four large goldfish? about 4″ ea.
Hi Belinda,
It is always a risk to keep large fish with shrimp or small crabs.
So, the real question is how high is that risk, and will you take it?
Personally, I would not do that.
In addition, Goldfish prefer low temperatures, unlike Pom pon crabs.
Best regards,
Michael
Hi Michael,
I’m a huge fan of this website, I wish I had known about this amazing resource when I got into keeping shrimp myself. My question is: are Pom Pom Crabs safe to keep in a Cherry Shrimp breeding tank, or will they consume shrimplets?
Also, do you have any plans to do a detailed care guide on Slipper Lobsters? I’ve been interested in breaking into saltwater with them but can’t find any good resources or information on keeping them online.
Hi Andrew,
Thank you for the kind words!
Regarding Pom pom crab and shrimp – I would not worry. They are one of the safest crabs you can have in a shrimp tank. They have never given me any trouble.
Slipper Lobsters is on my list. Even though they are not really popular in saltwater tanks.
Best regards,
Michael
Hello, do you think pom pom crabs will be fine with mystery snails? Thank you in advance.
Hi Riley,
I am pretty much sure that you won’t have any problems with Pom pom crabs and Mystery snails.
These crabs usually do not show any aggression.
Best regards,
Michael
From what I’m reading, it appears that these pom pom crabs have a life expectancy of about a year in an aquarium. It also appears that the young look very much like adults. Is there any way to tell a young crab from an older crab when purchasing one to help ensure a longer life span in the aquarium?
Hi Stan,
Unfortunately, I do not know any other way to tell the difference between young and old Pom pom crab but their size.
Best regards,
Michael
Are you able to keep pom pom crabs and dwarf crayfish together?
Hi Kaylee,
Personally, I would not keep Pom pom crab even with dwarf species like Cambarellus diminutus, Cambarellus shufeldtii, Dwarf Mexican crayfish (Cambarellus patzcuarensis), etc.
Best regards,
Michael
Can they live with micro crabs?
Hi Kristopher Goyette,
Yes, it is possible to keep Thai micro crabs and Pom pom crabs in the same tank.
Best regards,
Michael
Hi! Are pom poms social? Would it be a good idea to get a couple of them in a small tank or would they be fine on their own if I just got one?
Hi Adrienne Willoughby,
Personally, I have never had any problems with them.
I do not think that they will fight unless there are too many of them (1 pom pom crab per 2-3 gallons is ok), you do not have enough hiding places, and they are very hungry.
Best regards,
Michael
Is shipping stressful on these crabs? I’m hoping to order a few as I live where it is difficult to get any live aquatic things locally.
As I’ve already tried fish, hoping this invert could survive the trip.
This has been very helpful,
Thank you.
Hi Ake,
Unfortunately, shipping is stressful for all animals. It is just …from further away they are imported the worse they can tolerate it.
Best regards,
Michael
Will they be okay with a golden dojo loach? And do you have suggestions for safe acclimation to my aquarium water?
Hi Quinn,
I have never kept golden dojo loaches and pom pom crabs together, and I probably wouldn’t recommend it.
These fish can grow very large, and although they are not particularly aggressive overall, they can be nippy.
Best regards,
Michael
Would pom pom crabs be ok with dwarf mexican crayfish in a 10 gallon tank because I want to put them together
Hi Hunter,
I have been asked about this before, and my opinion has not changed at all – no, it is highly undesirable to keep Pom pom crab with any type of dwarf crayfish species. There is a high likelihood of conflict.
Best regards,
Michael
Hi Michael… My POM POM, Crab Pitt, got out of the little tank attached to my 50g. He has been in there for a month. But I didn’t see him the kast 2 weeks at all, thought he was too small and eaten by a Molly. But then Saturday, he was out running a muck. I was elated. So when I came Home today and my Sin said he was dead, I was crushed.
But, can u tell me, could it be his molted body? It was the front left leg and the empty body, even the little marks where his eyes are… or am I reaching and he is dead? I know u can’t be certain but mind venturing a guess?
Cheers!
Johnny
Hi Johny,
The empty exoskeleton will still have the shape of the crab, including the leg joints and eye marks. So, there’s a possibility that what you found could be the molted exoskeleton rather than crab’s actual body. 50g is a large tank for such a small crab, maybe he is hiding somewhere.
Best regards,
Michael