What do crabs eat in a fish tank?

In this post, we will answer the question “What do crabs eat in a fish tank?”. We will also understand what are the ideal conditions to raise crabs and also who their tank mates are.

What do crabs eat in a fish tank?

In a fish tank, crabs eat almost any food you offer them. Most of the crab species are omnivores. Which means that they eat a wide variety of food items. They may also act as scavengers and hunters, but only if the opportunity comes. Some of the items crabs feed on are:

–       Algae;

–       Shrimps;

–       Fish;

–       Insects;

–       Larvae;

–       Eggs;

–       Molluscs;

–       Vegetables

–       Suspended organic material.

Who are the crabs?

Crabs are crustaceans, invertebrate animals with an exoskeleton made of calcium carbonate. They need to exchange their carapace to grow. This process is called ecdysis, or moulting. To complete the ecdysis, the crabs need iodine and calcium supplement in the water.

There are different types of crabs, saltwater and freshwater ones. However, it is important to remember to keep structures on the surface, as some of them breathe atmospheric air on the surface.

Freshwater crabs

Freshwater crabs can be found in tropical and subtropical waters worldwide. There are more than 2,000 freshwater species in the world. The majority of these crabs are omnivores. Thus, they can generally be offered any type of food. We will consider three freshwater species to be raised in a tank:

–       Thai Micro crab;

–       Panther crab;

–       Pom Pom Freshwater crab.

Thai Micro Crab

The Thai Micro crab is also called False Spider crab. Its legs are very long in relation to the body, resembling a spider. This is a very small freshwater species called Limnopilos naiyanetri. In the wild, Thai Micro crabs can only be found in a river in Thailand. 

They are awesome additions to your tank. However, they are quite rare and difficult to find in pet stores. As few other crab species, they can live completely submerged. Due to its size, this unique species can live with many fish species and other tank mates. However, it is also important to remember that, due to its size, it can be chased by some aggressive fish species.

A nice tank for this crab species is a tank with plenty of hiding spots, like caves and plants. This crab feeds by filtering tiny suspended particles from the water column through hairs that cover its claws. Mostly algae, biofilm, and decaying plant material.

The recommended tank conditions to keep your Thai Micro crab is the 2-gallons minimum size, the temperature range between 72 and 82 degrees Fahrenheit, and pH between 6.5 and 8.0.

Panther Crab

The Panther crabs are a nice but very uncommon acquisition to freshwater fish tanks. This species, Parathelphusa pantherine, is classified as endangered due to habitat destruction and pollution. They are found in Sulawesi island, in Indonesia.

They are more active during the night and obtain most of their food by scavenging. Unlike the Thai Micro crabs, Panther crabs are territorial. Thus, they need a bigger fish tank to live and claim their territory, and having too many Panther crabs would also be an issue. A 20-gallon fish tank is ideal for this species. 

The recommendation for tank conditions is the temperature between 77 and 86 degrees Fahrenheit and pH between 7.5 and 8.5. An air pump is not necessary, although a filter is extremely important. Although they are fully aquatic, they also enjoy having dry land in the tank.

The best tank mates for Panther crabs are fast-swimmer shrimps, as the Cardinal Shrimp. As this species has a scavenging habit, they normally eat meat and vegetation. A varied diet is needed to keep your Panther crab healthy. They can also feed on dried food, which has low nutritional content. Thus, it is necessary to supplement with natural/live foods, such as brine shrimps and bloodworms. Vegetables are also good to offer to your Panther crab. Therefore, the plants you should keep in your tank are hardy plant species, because they can survive the damage caused by the crab.

Pom Pom Freshwater Crab

The Pom Pom crab’s scientific name is Ptychognathus barbatus. The Pom Pom name refers to its Pom Pom-shaped claws. Pom Pom crabs are incredibly pacific and no specificity is required to their tank, as they are hardy organisms. They live very well in community tanks.

They are an amazing addition to your tank. However, they are a bit rare to find in pet stores. These crabs are natural from African, Asian and Australian tropical waters. Pom Pom crabs are also scavengers. But, sometimes they can get some suspended food using their pom-poms. Feeding Pom Pom crabs in a tank can include protein-rich items, such as bloodworms.

An ideal tank for a Pom Pom crab includes plenty of hiding places, a minimum 5-gallon size, and peaceful tank mates. They are also fully aquatic creatures. However, they may spend some time on land if you provide them with space and structure. Water temperature should be between 68 and 78 degrees Fahrenheit and pH between 6.2 and 7.2.

Saltwater crabs

Saltwater crabs can be found in many marine environments worldwide. The majority of these crabs are omnivores. However, they are opportunistic hunters. We will consider three saltwater species to be raised in a tank:

–       Pom Pom Saltwater crab;

–       Halloween Hermit crab;

–       Scarlet Hermit crab.

Pom Pom Saltwater Crab

This Pom Pom crab in the saltwater version has different origins for its Pom Poms. While the freshwater Pom Pom crab pom poms are hairy structures on its claws, the pom-poms of the saltwater Pom Pom crab are anemones. These anemones can be species members from the Tractis or Bunodiepsis genera. 

The function of these anemones is to protect the crabs from predators and sometimes they can use these anemones to capture some food. The Pom Pom saltwater crabs are omnivores and typically feed on zooplankton. However, in a tank, it is possible to offer them dried foods and small shrimps.

This species is a low-maintenance species in a fish tank. Thus, Pom Pom crabs are also good additions to a tank. They do not require a large tank.

Halloween Hermit Crab

The scientific name of the Halloween Hermit crabs is Ciliopagurus strigatus. They get this name from their orange colour and red stripes patterns that resemble Halloween decorations. 

The Halloween Hermit crab is also an omnivore, can be a scavenger and an algae eater. They normally eat detritus, cyanobacteria and algae. For this reason, they can also be considered as good fish tank cleaners. They can get aggressive if the food is limited. 

As any other hermit crab, they own a shell and sometimes can kill snails to get a shell. Thus, it is recommended to provide different shells from time to time. A tank for this species should have at least 15-gallons and should provide rocky structures. This species is also nocturnal and during the day they hide between the rocky structures.

Scarlet Hermit Crab

The Scarlet Hermit crabs are very common among aquarists. These organisms are also part of the group of tank cleaners. They are low-maintenance and easy to raise. They are very peaceful individuals in relation to other hermit species.

The Scarlet Hermit crabs are herbivores. If you consider keeping some algae in your tank, keep in mind they may get attacked by your Scarlet Hermit crab. You can also offer them dried seaweed and some natural food. 

Similarly to the Halloween Hermit crab, they need some empty shells to exchange their “homes”. Therefore, providing them with new shells are recommended.

They are also very peaceful. However, it is highly recommended not to keep them with larger fish that might prey on these crabs. As small individuals, they can fit healthily in any tank size.

Breeding crabs in captivity

Breeding crabs in captivity is extremely difficult. Some owners might have limited reproductive success. However, captivity conditions are not ideal for pet crab species breeding.

Some species are rarer to find in the pet market. Thus, their price range can get very high. Most of the freshwater species are classified as endangered. And thus, they lost some of their popularity among tank owners.


In this post, we answered the question “What do crabs eat in a fish tank?”. We also learn some of the crab species, the ideal conditions to raise them in a tank, and their best tank mates.

If you have any thoughts or doubts, feel free to leave us a comment below!

Frequently Asked Questions (FAQs): What do crabs eat in a fish tank?

How long do freshwater crabs live in a tank?

The average lifespan of freshwater crabs is 3 years. However, some species can reach up to 10 years old. Providing ideal tank conditions may prolong your crab life.

Can I raise a Crab with a Betta fish?

No, keeping a crab with a Betta fish is not recommended. This is because of the aggressive behaviour of the Betta fish in the case of smaller crabs, and due to the crab’s aggressive or hunting behaviours towards the Betta fish.

Do crabs drown? 

Although some crab species are fully aquatic, others require partial living on land. This is because of their breathing requirements. Independently, providing proper habitat with terrestrial and aquatic environments is strongly suggested to sustain your crabs’ well-being.

Are crabs aggressive? 

Some of the crab species can get quite aggressive. They can dispute territory, and try to steal food from other animals. In addition, some crab species are opportunistic hunters. 

Are saltwater crabs easy to keep?

Saltwater Crabs are strongly recommended for beginners aquarists. They are generally low-maintenance organisms and typical members of the tank cleaners group. 

Do saltwater crabs need air?

However some crab species are fully aquatic, others require atmospheric air to breathe. Some hermit crabs cannot breathe atmospheric air nor in the waters. They require humid air, once they breathe through modified gills. 


Thai Micro Crabs (Limnopilos naiyanetri) https://aquaticarts.com/products/thai-micro-crabs

Panther Crab Care Guide & Species Profile. 2020. https://www.fishkeepingworld.com/panther-crab/

Freshwater Pom Pom Crab (Ptychognathus barbatus). https://aquaticarts.com/products/pom-pom-crab

Best Saltwater Crabs for Beginners – Fun to Watch! https://www.thebeginnersreef.com/best-saltwater-crabs-for-beginners-so-fun-to-watch/

Hermit Crab Care Guide & Species Profile. 2019. https://www.fishkeepingworld.com/hermit-crab/