The pom-pom crab (Ptychognathus barbatus) is a small freshwater crab that measures 1 inch (2.5 cm) in diameter or less.
Their “pom-poms” serve to hunt and capture food for the crab to eat, but they are still opportunistic feeders with other animals in the tank.
They love plants, can live in cooler or warmer waters, and do not need land access or substrate but will try to escape from the aquarium so be sure to have a secure fitting lid!
In this article
At a Glance
|Adult size:||1 inch (2.5 cm)|
|Minimum tank size:||5 gal (20 l)|
There is little information available for the pom pom crab.
However, what is known is that they can be found in the tropical areas of Asia and Africa, including Madagascar and Taiwan.
Color and Appearance
Not to be confused with the anemone-loving saltwater pom pom crab, freshwater pom pom crabs are very different.
Appearance-wise, these crabs look quite similar to Thai micro crabs.
They are a light brown color with light gray, black, and white markings. Their legs are about the same length as the carapace.
The most unique quality of this crab is the “pom-poms” that they have on both claws. The fluffy, hair-like tufts serve a purpose, they catch and collect small particles of food for the crab to eat.
These crabs typically max out at around an inch (2.5 cm), but some can grow an extra half an inch when given the right care.
Behavior and Tank Mates
Pom pom crabs are quite peaceful and tend to leave other tank mates alone.
That being said, they are still opportunistic feeders and may still go after the occasional fish, shrimp, or snail. However, this is rare and the crabs usually remain peaceful.
Other invertebrates are the best option regarding tank mates, but non-aggressive, fast-moving fish that occupy the top or middle water column may work as well.
Pom pom Crab Tank Setup
Pom poms prefer a more neutral pH compared to other species. 6.5 to 7.5 is a good range for them.
Temperature-wise they can live in cooler or warmer waters and can withstand temperatures up to 80°, but no less than 68°.
5 gallons (20 l) is the absolute minimum. If you are planning on housing multiple pom poms or multiple species, 10 gallons or more will be needed.
Fully aquatic, this crab does not need access to land, but will still try and escape from the aquarium so be sure to have a secure fitting lid.
Since they don’t bury themselves to molt, soft substrate is not needed. Small gravel, river rock, and coarse sand are all viable options.
Pom pom crabs do not require dense vegetation in their tank, but live plants are still a must. Decaying plant matter and detritus is an important (and free!) food source.
These crabs love aquatic mosses, like marimos. The moss provides an excellent place for foraging as loose food tends to collect in the plant.
Food and Diet
Unlike most other crabs, vegetation makes up a pretty big portion of the pom pom’s diet.
They feed on detritus and algae and any food particles that get caught in their “pom-poms”.
Plant-based invertebrate pellets and wafers are a big hit!
Meat-based foods should be fed less often but still regularly. Bloodworms and other micro worms are high in protein and good for those limited, meat-based meals.
Pom pom crabs only breed in brackish water, and their young can not survive in freshwater.
Other than that, not much else is known about their breeding practices.
Whether you are looking to add a new crab to your tank, or want to take an existing species into a new home, I hope this guide will help you out!
Leave a comment below if you’ve ever kept pom pom crabs and have any advice to add!