The Fiddler Crab is one of the most interesting invertebrates for fish keepers who want to explore caring for species other than fish. They have unique physical traits and lively personalities.

If you are an aquarist who has only ever cared for fish, you’ll be surprised at the number of things you have to learn about in order to properly care for a Fiddler Crab.

With time and dedication, you should be able to master the Fiddler Crab’s unique needs and aid them in living healthy, happy lives for as long as possible.

In this article, we’ll introduce you to the Fiddler Crab, its physical traits, behaviors, and preferences. Our experts will share their knowledge on setting up a tank specifically made for Fiddler Crabs, as well as how and what to feed them.


Before we dive right into the action of caring for Fiddler Crabs, there are some facts and figures about this crustacean that you need to keep in mind. Below is a table you can use as a quick reference to get to know the Fiddler Crab a little better.

Family Ocypodidae
Genus Uca
Size 2 to 3 inches in width
Lifespan Up to 1.5 years (in a freshwater environment)
Temperament Peaceful
General Community Behavior Thrives best in a dedicated tank
Minimum Tank Size Required 10 to 15 gallons

Fider Crab Background

The Fiddler Crab is also sometimes called the Calling Crab. The name “Fiddler” is taken from the male crab’s distinctive appearance. Male Fiddler Crabs have one claw that is significantly bigger than the other. This larger claw is thought to resemble a violin and has many uses when it comes to feeding and breeding.

– Crabby Origins

The Fiddler Crab can be found in several regions throughout the world. There are Uca Crabs in both the Pacific and Atlantic areas of the globe. These crabs can be easily found in marshes, mangroves, mudflats, and even the sandy beaches of West Africa. The Fiddler Crabs’ original habitats are mostly in what we call brackish waters.

The term “brackish” refers to a condition of water being saltier than normal freshwater bodies but significantly less salty than true saltwater forms. This is crucial information to retain if you truly intend on caring for Fiddler Crabs.

Some hobbyists mistakenly think that Fiddler Crabs can be raised in the same freshwater environment as most fish. However, this is simply not the case; in fact, the insistence on treating Fiddler Crabs as freshwater creature has proven to be detrimental to their health and lifespan.

– The Fiddler Crab’s Physical and Behavioral Traits

Now that you know where Fiddler Crabs come from, you can get to know more about their physical and behavioral makeup. Familiarizing yourself with the Fiddler Crab’s appearance and behavioral quirks will help you anticipate and prevent potential challenges later on.

– Physical Appearance

Fiddler Crabs are different from freshwater fish mainly because they are semi-terrestrial. This means that they alternate from staying submerged in cool water to sitting on warm sand or strips of land.

These crabs have orange or brown shells that change depending on the environment or social cues given by other Calling Crabs. There is also the Blue Fiddler Crab, otherwise known as the Pacific Fiddler Crab, which is particularly eye-catching due to the bright blue color of its shell.

Like other crabs from the Uca genus, Fiddler Crabs have ten feet on which they scuttle and sit. Male Fiddler Crabs are sometimes remembered as the crab with big claw, whereas the females have smaller claws.

A male Fiddler Crab can use its larger claw to attract mates or fight with other males to establish territory and dominance. On the other hand, due to having similarly-sized small claws, a female Fiddler Crab is much faster and more efficient than her male counterpart when it comes to sifting the sand for potential food.

– General Behavior

Fiddler Crabs are relatively peaceful crustaceans. They are small crabs that work best in groups. You can easily house four young Fiddler Crabs in a small tank with a capacity of about 10 to 15 gallons.

However, if you want to raise more than four crabs at once, you need to invest in larger tanks. The more space you can provide for these social crustaceans, the more harmonious their behavior around each other (except, of course, when they are choosing their mates and establishing burrowing grounds).

As mentioned previously, male Fiddler Crabs rely on their larger claws to attract mates. They will wave these larger claws around in hopes of getting the attention of female Fiddler Crabs; the larger their claws, the more likely they are to win over a female.

The males will also use these larger claws to thwack and grip other male challengers who might be interested in the same breeding spot or female. Fiddler Crab fights can get quite hectic, so it is not uncommon to see some males come out of a fight with damaged large claws.

Basic Care Notes for Fiddler Crabs

By now, you already know that Fiddler Crabs are amazing creatures with territorial tendencies. That said, how do you care for these crabs in the comfort of your home? In this section, we’ll cover what you need to prepare for your Fiddler Crabs as well as teach you about what and how to feed them.

– Preparing a Fiddler Crab-Friendly Environment

The first thing you need to prepare before you bring home your new batch of Fiddler Crabs is their tank or enclosure. When choosing an aquarium for your Fiddler Crabs, be sure to consider not just the capacity of the tank in question but its width and length as well.

Remember that these creatures are used to scuttling across sandy beaches and muddy mangroves. They need more horizontal space than they do vertical space.

Choose the largest tank that you can afford and that can fit in the confines of your home. The larger the tank, the healthier and happier your Fiddler Crabs, will be in the long run. In addition, do not forget to choose a fine mesh cover for your tank to prevent your crabs from escaping and any other unwanted creatures from entering the aquarium.

– Setting up the Tank

Fiddler Crab tanks are different to set up when compared to your usual freshwater fish. This is because your Fiddler Crabs won’t spend all of their time in the water. That said, you will need to create a small shore for them, or at least a place where they can come up to rest on a solid strip of substrate.

Be sure to choose a substrate that has sandy or fine particle qualities; do not use gravel as your tank substrate because this will harm your crabs and make it difficult for them to forage.

Some aquarists accomplish this by filling half of the tank with only two inches of substrate and then pouring the rest of their chosen substrate on the other half of the tank. This effectively divides the tank into two areas: one half that is mostly water and one half that is mostly substrate. You can then decorate your tank with aquarium plants, driftwood, and rocks.

– Achieving Brackish Water Conditions

Once you have finished the layout for your Fiddler Crab enclosure, you need to put effort into mimicking the brackish water conditions that make up most of their natural habitat. This is the key to maximizing your Fiddler Crab lifespan.

Below is a table you can use as your quick guide to creating ideal water conditions for your Fiddler Crabs.

Temperature 75 to 85 degrees Fahrenheit; 23 to 29 degrees Celsius
pH Level 8.0 to 8.5
Water Hardness Level 15 to 30 dKH
Salinity 1.01 to 1.08
Light Level Medium intensity only for additional warmth

Additional notes: Do not use plain freshwater when building your Fiddler Crab enclosure. Instead, you can mix about one-fourth cup of marine salt for every two liters of water in your tank.

Then, use a hydrometer to find out the salinity level of the water and adjust as necessary. In addition, consider investing in a high-quality air pump or filter outlet to help in keeping the water aerated for your Fiddler Crabs.

– Make Way for Molting Crabs

Another thing to keep in mind when you care for Fiddler Crabs is that they go through a process called molting. Every eight weeks or so, an adult Fiddler Crab will molt or shed its shell.

While the actual shedding of the shell only takes around 15 minutes to complete, the molting process actually begins ten days prior to this biological change.

Molting helps your Fiddler Crabs renew their exoskeletons or shells. This is particularly useful for male crabs that have dented or cracked their shells during territorial or mating disputes. During your Fiddler Crabs’ molting season, be sure to supplement their diet with calcium and water to help them recover fully.

– Diet Tips for Fiddler Crabs

Once you have a suitable enclosure prepared for your Fiddler Crabs, you can then focus on creating a balanced diet for them. Fiddler Crabs are considered omnivorous, so this opens up quite a few food choices for you to play around with until you find a combination that is both sustainable and nutritious. Take a look at our experts’ notes on what and how often they feed their Fiddler Crabs.

Commercial Crab Pellets

You can easily acquire crab pellets from your local fish store. These pellets are designed to sink to the bottom of the aquarium, encouraging your Fiddler Crabs to sift the bottom layer to collect food. These pellets can make up around 40 to 50 percent of your Fiddler Crabs’ diet.

Frozen Food

Another type of food you can easily access and feed your Fiddler Crabs is frozen food. You can purchase frozen brine shrimp, plankton, bloodworms, and other small insects. This will help you mimic the natural diet that your Fiddler Crabs would have feasted on in the wild. Aim to feed frozen, protein-rich food to your Fiddler Crabs in such a way that it makes up 20 to 30 percent of their diet.


Fiddler Crabs also appreciate the occasional servings of vegetables. While this type of food should not replace their main intake of pellets and protein-rich food, they are a nice supplement and source of extra nutrients for your Fiddler Crabs. Some of the vegetables you can safely feed to your Fiddler Crabs are pieces of boiled zucchini and lettuce.

– The Most Suitable Fiddler Crab Tank Mates

If you decide to keep more than one Fiddler Crab in a single enclosure, be sure to maintain a ratio of 1 male to 4 females. This will prevent most mating and territorial fights from becoming too aggressive. On the other hand, if you plan to introduce other aquatic inhabitants to your Fiddler Crab tank, you will have to select them more carefully.

Below is a list of our top recommended tank mates for your Fiddler Crabs.

1. Mollies

Mollies are often exclusively thought of as freshwater fish. However, Mollies are such hardy fish that they can actually adapt to alkaline water, reef water, and even other types of hard water. That said, raising Mollies in the same brackish water tank as your Fiddler Crabs would not pose a problem at all.

Most Mollies grow to a maximum length of three inches, and they are all agile swimmers. This means that should your Fiddler Crabs feel feisty, your Mollies will be able to swim away without being harmed. You might want to consider Black Mollies, in particular, to serve as companion fish to your Fiddler Crabs.

2. Gobbies

Gobbies are another type of fish often mistaken to be purely freshwater fish. In reality, a large number of Goby species actually fare better in brackish water compared to freshwater conditions. That and their naturally peaceful nature make them great candidates to share your Fiddler Crabs’ space.

Some interesting Goby species that you might want to include in your Fiddler Crab tank are the attractive Bumblebee Goby and the shy Violet Goby.

3. Swordtails

Swordtails are colorful and hardy fish that enjoy brackish water. They would naturally fit in well with your Fiddler Crabs. Swordtails are generally passive and will do their best to stay out of the way of other aquarium inhabitants.

Swordtails can grow to about 5.5 to 6 inches in length. If you decide to include them in your Fiddler Crab tank, be sure that there is more than enough space for these fish to swim in the portion of the aquarium that is submerged in water. Too cramped a swimming space will stress these fish out and could lead to them becoming sickly.

4. Amano Shrimp

If you want to have other invertebrates in your Fiddler Crab tank, you can introduce Amano Shrimp to the party. Amano Shrimp love brackish water and will feel right at home in an enclosure designed for Fiddler Crabs.

This type of shrimp is peaceful and grows to about the same size as Fiddler Crabs. This makes it less likely that the Fiddler Crabs will prey on the Amano Shrimp. This type of shrimp is mostly herbivorous and will help in keeping your tank clean of floating excess food or debris.

Breeding Fiddler Crabs in Captivity: Is it Possible?

Unfortunately, breeding Fiddler Crabs in captivity is impossible. This is because there are many factors that are necessary for a successful Fiddler Crab mating.

One of the key aspects that must occur during a breeding season is for the Fiddler Crab eggs to be laid in the depths of the ocean. This is necessary because the larvae that hatch from the eggs are planktonic; they need to spend some time in the depths of the ocean before finding their way back to land.

Such breeding and hatching conditions cannot be mimicked in simple home aquarium setups. That said, even the most experienced aquarist will be hard-pressed at breeding Fiddler Crabs.

Some hobbyists have witnessed Fiddler Crabs perform mating dances and even lay their eggs in their home tanks. However that is as far as it gets. Some of Mother Nature’s environments and processes are simply too difficult to replicate by mere humans.

Final Thoughts on the Fiddler Crab

We learned so many things about the small but wonderful Fiddler Crab. Here is a quick rundown of the most important points we tackled in this article.

  • Fiddler Crabs are small, semi-terrestrial crustaceans.
  • They thrive in brackish water, though they are most often mistaken as freshwater crabs.
  • Male Fiddler Crabs are known for having one large claw that they use for mating and fighting.
  • Though Fiddler Crabs do fine in dedicated tanks, you can include Mollies, Gobies, and Amano Shrimp in their enclosure as well.
  • Fiddler Crabs cannot be bred in captivity.

Now that you know all there is to know about Fiddler Crabs, you can apply what you’ve learned here to set up the best environment for your new crustaceans. Caring for Fiddler Crabs doesn’t require too much attention, but it does take some getting used to. Keep what you’ve learned from this article in mind, and you’re sure to be well on your way to raising Fiddler Crabs with success.

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