When creating a freshwater aquarium ecosystem, there is no better creature to add than a freshwater crab. With spitfire personalities, incredible intelligence, easygoing tank preferences, and vibrant colors, freshwater crabs are guaranteed to improve any tank you create.
However, like all living things, freshwater crabs require specific habitat characteristics to survive. The following article outlines care requirements for freshwater crabs, as well as the best freshwater crabs to keep in your aquarium.
Table of Contents
Benefits Of Aquarium Crabs
Every crab you introduce to your freshwater aquarium will bring its own personality, requirements, and challenges. However, crabs generally provide far more benefits than hardships when added to your aquarium, including:
- Scavenging Behaviors. Crabs spend their days moving around the tank and consuming leftover fish food, waste, algae, and dead plant matter. Crabs help you keep your tank clean and decrease the amount of maintenance that your tank requires.
- Entertainment. Crabs are curious, active creatures that will brazenly explore every inch of the tank that they can reach. As such, your tank will never lack for movement and excitement.
- Color and Diversity. Crabs are typically brightly colored with whimsical eyes, mouths, and claws. Where your fish are flowing grace, crabs are all sharp angles and intentional movement, bringing complementary patterns to the forefront of your habitat.
Crab Habitat Requirements
As with any other individual you add to your aquarium, the habitat requirements for crabs are species-dependent. However, most crabs typically thrive in the following tank conditions:
Tank
If you are housing a single crab, most crabs can be housed in a 5-10 gallon aquarium. However, if you plan on having multiple crabs or other species, your tank should be at least 10 gallons in size. Make sure you consider the size that your crab will reach in adulthood, not its current size when choosing a tank.
Tank Cover
Crabs are master escapers that put Houdini to shame. They can climb decorations, pipes, tubes, chords, and fish, and even swim small distances. Before adding crabs to your freshwater aquarium, make sure you have a lid that seals and a tank net to protect your crabs from climbing your filters or skimmers. Before opening or closing the lid of the tank, make sure that you check the whereabouts of your crabs to watch for potential escapees.
Dry Land
Most crabs require both dry and submerged areas to survive. They, therefore, thrive in paludarium aquariums, which incorporate terrestrial and aquatic elements.
If you do not have a paludarium setup, most crab species are content with a floating perch or sloping substrate that gives them sufficient dry land. When creating a habitat for your crab, most species prefer two parts water to every one part dry land.
Water Conditions
When considering water conditions for a crab, it is important to look at temperature, pH, and salinity. In general, freshwater crabs prefer warm waters that are 72-82o Fahrenheit. Most crab species are relatively hardy when it comes to pH, though some prefer slightly more acidic water.
The most important water condition to monitor is salinity. While most of the species on this list thrive in freshwater environments, there are several that prefer brackish water (water that has a low salt content). If you are adding your crab to a freshwater tank, make sure you choose a freshwater species.
Whenever you add water to a crab habitat, it is important to make sure that you filter the water prior to adding it. While tap water is safe for us to drink, the chemicals in the water, such as chlorine, are toxic to crabs.
Decorations and Hiding Places
If you want your crabs to thrive in your aquarium, you want to create an environment that mirrors their natural habitat. In the wild, crabs survive by camouflaging and hiding in the plants and rocks that surround them.
Crab habitats are your chance to achieve all of your decoration dreams. The more places crabs have to hide and explore, the happier they will be.
Calcium
Crabs use calcium to harden their shells. If there is not enough calcium in their environment, they are not able to molt and grow. Adding calcium supplements to the tank will ensure that they are getting the calcium they need to thrive.
Crab Tankmates
Most crabs are relatively peaceful creatures, making them ideal additions to multi-species aquariums. Though some crab species get along with their neighbors better than others, most crab species will live harmoniously as long as you follow these guidelines:
- Don’t house your crabs with aggressive or territorial fish, such as cichlids.
- Don’t house your crabs with fish that they can be aggressive towards, such as small fish, frogs, or scavenger fish.
- Consider fish that prefer the top half of your tank. Fish that prefer to stay in the upper and middle water columns will rarely come into contact with your crabs, thereby minimizing the chances of aggression and predation between the species.
- Crustaceans can be territorial. If you plan on housing multiple crabs together, ensure you provide them with sufficient tank area and hiding spaces to minimize aggressive behaviors.
1. Red Claw Crabs
- Experience Level: Beginner
- Temperament: Peaceful
- Maximum Size: 4.0″ leg span
- Lifespan: 5 years
- Diet: Omnivore
Red Claw Crabs are one of the most popular freshwater crab species in the aquarium trade. As their name suggests, Red Claw Crabs are typically red or maroon, with bright red claws. They are shy, skittish crabs that do well in peaceful tank environments.
While Red Claw Crabs can live in freshwater, they actually live in brackish water in the wild. If you want your Red Claw Crabs to not only live but thrive, you will need to add aquarium salt to your tank. Ideally, Red Claw Crabs prefer brackish water with a specific gravity of 1.005.
Red Claw Crabs are great starter crabs due to their hardy natures and low costs. They are easygoing when it comes to water conditions and, in general, are happy as long as they have a clean tank and a regular feeding pattern.
Like most crab species, Red Claw Crabs require a land area. However, they do not spend as much time on land as many of the other freshwater species, and therefore require less land space than many of the other species on this list.
Red Claw Crabs are extremely territorial and should, therefore, only be housed singly or in a large tank so that each crab has plenty of space. However, Red Claw Crabs are peaceful with other species and are therefore great for community tank environments.
2. Thai Devil Crab
- Experience Level: Beginner
- Temperament: Peaceful
- Maximum Size: 2.0-3.0″ leg span
- Lifespan: 5-15 years
- Diet: Omnivore; enjoy brined fish, insects, dried algae, and fruits and vegetables
Don’t be alarmed- these crabs get their name from their appearance, not their personality. Thai Devil Crabs, also known as Black Devil Crabs and Purple Thai Devil Crabs, are so named for their pitch-black or deep red carapaces.
Thai Devil Crabs are docile, yet energetic creatures. They are ideal for active tanks with friendly, non-confrontational tankmates. They coexist well with others and will happily spend their days scavenging around the tank. As exceptionally hardy crabs, they do well in a wide range of tank conditions.
Thai Devil Crabs require both terrestrial and aquatic sandy substrates because their natural tendency is to burrow for safety. Without sandy substrates, even the safest Thai Devil Crabs may feel stressed. They also prefer habitats with plenty of decorations to camouflage and hide in.
3. Vampire Crabs
- Experience Level: Intermediate
- Temperament: Peaceful
- Maximum Size: 1.0-2.0″ leg span
- Lifespan: 3 years
- Diet: Omnivore
Unlike Thai Devil Crabs, Vampire Crabs are so named for both their striking appearances and unique personalities. Vampire Crabs are primarily nocturnal crabs that have deep purple or red shells with bright yellow eyes. When you see them stalking around the tank in the dark, their yellow eyes glowing, it is easy to see the Vampire-like resemblance.
Vampire Crabs are one of the most exotic species on this list, which makes them both more expensive and harder to find. However, the added difficulty is certainly worth the reward. These friendly, eye-catching crustaceans are a beautiful addition to peaceful communities with other small inhabitants.
At only 1.0-2.0 inches at adulthood, Vampire Crabs are easy targets for larger fish. As such, it is best to house them with smaller fish that won’t consider them food. If they are in a tank with larger fish, it is important to provide them with plenty of hiding spaces.
Vampire Crabs require sandy substrates and plants in both the terrestrial and aquatic areas of their tanks. In addition to using the substrate as a hiding place, Vampire Crabs also burrow in the sand during their molting period to protect themselves from predators.
4. Panther Crab
- Experience Level: Intermediate
- Temperament: Semi Aggressive
- Maximum Size: 3.0-4.5″ leg span
- Lifespan: 5 years
- Diet: Omnivore
As their name suggests, Panther Crabs are bright orange crabs with black spots. Like the big cats from which they get their name, Panther Crabs should be housed singly or in pairs, as they are aggressive towards other Panther Crabs.
If you want multiple Panther Crabs in your aquarium, make sure you only keep one male with multiple females to prevent competition during mating season. It is easy to identify male Panther Crabs because they have one claw that is much larger than the other one. This large claw is used for courtship and competition.
Panther Crabs are generally friendly towards other fish, though they have been known to eat tankmates if they are not properly fed. Therefore, if you want to keep them in a community tank, it is best to house them with larger fish and keep them on a very consistent feeding schedule.
Panther Crabs spend the majority of their time underwater. As such, they require a smaller terrestrial area than most crabs, making them an easy species to introduce to an existing community aquarium.
5. Matano Crab
Image Source: https://praquatics.com/forums/threads/purple-matano-crab-syntripsa-matannensis.4119/
- Experience Level: Beginner
- Temperament: Slightly Aggressive
- Maximum Size: 3.0-5.0″ leg span
- Lifespan: 2-3 years
- Diet: Omnivore
Matano Crabs, also known as Golden Leg Matano Crabs, are large freshwater crabs relatively new to the freshwater aquarium circuit. They are large crabs with square carapaces that make them appear adorably chunky. They are typically solid purple with bright white leg joints.
Matano Crabs are quickly becoming popular because, unlike most freshwater species, they are fully aquatic, meaning that they do not require a terrestrial component in their tank. This means that they are very easy to add to established community aquariums.
Though they are relatively hardy, Matano Crabs do require water conditions that are more specific than most freshwater crab species. They prefer tanks that are 77-86o F with a pH of 7.8-8.2. To keep water conditions from being too variable, it is best to introduce Matano Crabs to established community tanks instead of adding them initially.
Matano Crabs are fairly large and will prey on smaller fish within reach. As such, they are best paired with larger or quicker fish that primarily reside in the middle and upper water columns.
6. Fiddler Crab
- Experience Level: Beginner
- Temperament: Peaceful
- Maximum Size: 2.0″ leg span
- Lifespan: 2-3 years
- Diet: Omnivore
Chances are you’ve seen Fiddler Crabs on nature documentaries or in aquariums. Fiddler Crabs are easily identified by their large dominant claw, which they use for communication, mating, and fighting. These crabs are named Fiddler Crabs because when they eat with their smaller claw, it looks like they are playing their large claw-like a fiddle.
With over 100 different species of varying colors, the Fiddler crab family is one of the most popular crabs for freshwater tanks. Their hardiness and ease of availability, along with their adorable nature, make them the perfect starter crab for a community tank.
Like Red Claw Crabs, Fiddler Crabs can survive in freshwater. However, they prefer slightly brackish water with a salinity of 1.001 and 1.008. They spend a large portion of their time out of water, so a large terrestrial area in the tank is a must.
Fiddler Crabs are incredibly social creatures that prefer to travel in groups. As such, you should never house them singly. Because of their social nature, Fiddler Crabs are easy tankmates that thrive in most peaceful community tanks.
7. Rainbow Land Crab
- Experience Level: Beginner-Intermediate
- Temperament: Semi-Aggressive
- Maximum Size: 6.0-8.0″ carapace
- Lifespan: 8 years
- Diet: Omnivore
If you’re looking for a crab that cannot be missed, the Rainbow Land Crab is the perfect crab for you. Rainbow Land Crabs, also known as Halloween Crabs and Moon Crabs, are about 8.0 inches in diameter when fully grown, making them the largest crab on the list.
Because of their immense size, Rainbow Land Crabs require a tank of at least 30 gallons. As their name suggests, they spend most of their time on land, so they need a large terrestrial area as well.
Rainbow Land Crabs are hardy and will survive in nearly any habitat. They prefer habitats with muddy substrates so they can burrow, and thrive in freshwater or brackish water.
Due to their size, they can be a bit aggressive towards smaller species. As such, it’s best to house them with larger species that they cannot bully or eat. However, they are generally peaceful tankmates and are a striking addition to any freshwater or brackish water habitat.
FAQs
Can I Put a Freshwater Crab in My Fish Tank?
The simple answer is yes! Most freshwater crab species are peaceful and will happily coexist with fish in a tank. However, certain crabs and fish will eat one another, so it is important to make sure you choose the best crab species for your habitat. For more information, see our favorite crab species above.
Will a Freshwater Crab Eat My Fish?
Freshwater crabs are omnivorous, so they do occasionally eat fish. The easiest ways to keep your crabs from eating your fish are:
- Feed your crabs consistently so that they are not hungry.
- Keep fish that are large enough to not be mistaken as food.
- House crabs with fish that live in the upper and middle water columns to minimize fish-crab interactions.
What Do Freshwater Crabs Eat?
Freshwater crabs are omnivores, which means they eat plant and animal matter. A freshwater crab’s diet should subsist of store-bought flakes, pellets, or frozen food.
You can supplement the store-bought food with brine fish, insects, dried algae, and fresh or dried fruits and vegetables. Your crabs will also enjoy scavenging your tank for algae, dead organic matter, leftover fish food, and fish waste.
Do Freshwater Crabs Need Air?
Yes, crabs can breathe air both in and out of water. Crabs breathe by passing water over their gills, just like a fish. As the water passes the gills, the crab is able to pull oxygen into its bloodstream through osmosis.
However, unlike fish’s gills, crabs’ gills also allow them to breathe out of water. As long as their gills stay damp, oxygen can diffuse from the atmosphere into the water, and then be absorbed into their bloodstream.
Can Freshwater Crabs Live Underwater?
Freshwater crabs are aquatic or semi-aquatic, meaning they spend some or all of their time underwater. Most crabs spend time on dry land each day to rest, scavenge, and burrow.
How Do I Determine the Gender of My Crab?
For some crabs, such as Fiddler Crabs and Panther Crabs, males are distinguished by one enlarged claw, which they use for courtship and competition.
However, all crabs can be sexed by examining the bottom of their carapace. When you look at the bottom of your crab, the male will have a narrow bottom plate that is triangular in shape, while the female has a wide, round bottom plate to hold eggs.
How Long Do Freshwater Crabs Live?
The lifespan of a freshwater crab is entirely dependent on its species and habitat quality. In general, freshwater crabs can live anywhere from two years (Fiddler Crabs and Matano Crabs) to 15 years (Thai Devil Crabs).
Final Thoughts
Crabs are generally resilient, easygoing creatures that can be introduced to a range of habitats and tankmates. However, the more research and work you do, the happier your crab will be in its new home.
Whether you’re starting a crab aquarium or adding a crustacean to a community tank, freshwater crabs are an excellent animal to purchase. They are inquisitive, energetic, friendly, and eye-catching, providing endless entertainment as they go about their lives.
