Fiddler Crab

The Ultimate Fiddler Crab Care Guide

Are you an aquarist looking for a change from keeping fish? The fiddler crab may be what you are looking for. Hardy and engaging, these two-inch creatures are low-maintenance and can live for three years in captivity.

Fiddler crabs get their name from the males’ distinctive claws. The males have one claw that’s much larger than the other one, held in a way resembling a fiddle.

Though fiddler crabs aren’t difficult to keep, you need to know some important facts to keep them successfully.

Setting up the Habitat

Consider the environmental conditions in the fiddler crab’s natural habitat when creating your aquarium setup.

What Kind of Environment Do Fiddler Crabs Need?

These crabs are found among mudflats and brackish waters. You’ll want to mimic these conditions in your fiddler crab’s aquarium setup as follows.

Water Conditions for Fiddler Crabs

Fiddler crabs inhabit brackish waters, a term for water with a higher salt content than freshwater but less than ocean water.

To create brackish water, purchase aquarium salt and a hydrometer from a tropical fish store. You should be able to achieve the right salinity by adding a tablespoon of aquarium salt per five gallons of water.

A hydrometer is an inexpensive instrument that measures the salinity of water, also known as specific gravity. The specific gravity of the water should be between 1.005 and 1.01.

Important Note: While fiddler crabs need to be provided with water, they aren’t the best swimmers, so the water depth only needs to be a few inches. Other water parameters for your fiddler crab include the following:

  • The temperature of the water should be between 75 and 85 degrees Fahrenheit.  You can achieve this temperature using an aquarium heater.  If needed, you can also provide the tank with a heat lamp positioned over the tank.
  • The pH of the water should be between 8.0 and 8.3.
  • The water hardness should be 12 to 30 KH. 

Fiddler Crab Housing

A 10-gallon aquarium makes a good enclosure for fiddler crabs, and it will be big enough to house up to four crabs. For more than four crabs, increase the tank size by five gallons for each additional crab. Also, provide the tank with a secure lid to keep your crab from crawling out of the tank.

Substrate for Fiddler Crabs

Though fiddler crabs are aquatic, they need a dry area to burrow in. For this reason, build a beach in the aquarium using an aragonite or sand substrate.  

Don’t use gravel as it’ll be too coarse for your fiddler crab.

Gravel is also not fine enough to allow fiddler crabs to scavenge or borrow. If you use aragonite, it will help maintain the pH levels and provide trace minerals for your pet to keep them healthy. 


I recommend adding an aquarium filter to help maintain the water quality. When selecting a filter, choose an internal filter as opposed to an external filter. Fiddler crabs have been known to use external filters to climb out of aquariums.  

If you use a filter, you’ll still need to do a 20% water change every one to three weeks, depending on the number of crabs that you have in the tank. If you have more than one crab in a 10-gallon aquarium, you’ll want to do  a weekly water change. If you don’t use a filter, do a 20% water change every few days and add an air stone to keep the water aerated.

Fiddler Tank Plants and Decorations

After you create a beach and water area for your fiddler crab, complete it by adding plants and decorations, such as driftwood and small rocks. The plants and decorations will be most needed in the water area, as your fiddler crab will use them to climb out of the water when needed.

Small plants can be added to both the beach and bathing area. When placed in the beach area, plants can provide shade. You can use artificial plants for this purpose.

Maintaining the Fiddler Crab Habitat

A major part of providing fiddler crab care is to perform water changes every few days or weeks if you provide filtration. Additionally, you need to replace any evaporated water with fresh water to maintain the right salinity. Use a hydrometer to check and make sure.

Best Fiddler Crab Tankmates

Because fiddler crabs live in brackish waters, their tank mates need to be able to tolerate the same conditions. Based on this, the following are the best tank mates for fiddler crabs:

Bumblebee Goby (Brachygobius xanthozonus)

A peaceful fish from Indonesia and Thailand, the bumblebee goby is an excellent tank mate for fiddler crabs. They’re small-sized, only reaching one and a half inches in length, have the same water parameters as fiddler crabs, and won’t compete for food with your fiddler crab. Bumblebee gobies eat tubifex and blood worms, which you can buy live or frozen.

If you decide to go with bumblebee gobies, get at least six of them as they feel safer when they’re kept as a group. It’s important that you provide these fish with plenty of hiding places, which can be in the form of rocks, driftwood, or plants.

Endler’s Livebearer (Poecilia wingei)

Native to Venezuela, these colorful, small fish don’t require much space and do well with fiddler crabs. Endler’s livebearers can tolerate a range of water parameters and help keep the tank clean as they’ll scavenge. They eat flake food and are prolific breeders.

Leopard Guppy (Poecilia reticulata)

This colorful species is from South America and does well with fiddler crabs. Leopard guppies are a hardy species and can live in a wide range of water parameters. The only drawback is that these one-inch fish may be confused as food by your fiddler crab, so it’s important to keep your fiddler crab well-fed.

Double Swordtail Guppy (Xiphophorus helleri)

Found in Central America, these striking colored fish are another species that’ll do well with fiddler crabs as they can be kept in a broad range of water parameters. These omnivorous fish will eat flakes, pellets, and frozen food. The one thing to consider is that they grow up to six inches long and readily breed in captivity so you’ll need to make sure your tank is an appropriate size.

Mollies (Poecilia Sp.)

Mollies belong to the same family as guppies and swordtails. These fish are hardy and do well in fresh, brackish, and even salt water. They grow to around three inches, and they do well with fiddler crabs. Found from the Southern United States to Southern Mexico, Mollies are mainly grazers, so they should be fed a commercial diet that contains plant matter. Mollie diets are available at tropical fish stores.

Fiddler Crab Tank Mates to Avoid

The species of fish or invertebrates that would not make good tank mates for fiddler crabs are any species that require water parameters that are different from those of fiddler crabs. Also avoid larger carnivorous fish or smaller slow-moving species.

The following are some fiddler crab tank mates that you should avoid:

  • Pufferfish
  • Cichlids
  • Gobies (other than bumblebee gobies)
  • Siamese  tiger fish

Fiddler Crab Behavior

In the wild, fiddler crabs are as comfortable underwater as they are on land. When the tide comes in, they spend their time underwater. When the tide goes out, they’ll burrow in the sand, where it’s moist. They can do this because of an interesting aspect of fiddler crab anatomy—they’re equipped with both gills and a primitive lung.

Besides burrowing in the sand, fiddler crabs will explore the mudflats as they search for food. As a form of communication, male fiddler crabs will wave their enlarged claw to notify other male crabs of their presence.

Fiddler crabs molt about every two months, where they shed their exoskeleton to reveal a new one. They should be handled as little as possible as it’s stressful for them.

What Should I Feed My Fiddler Crabs?

Fiddler crabs are omnivorous. In the wild, they sift through the sand  in search of organic matter, such as algae, fungi, and other small organisms. They should be fed once a day and any remaining food should be removed the following day. The following are recommendations for a fiddler crab diet:

Commercial Crab Pellets

Crab pellets can be purchased at tropical fish stores. These pellets will sink to the bottom of the tank, allowing your crab to sift the substrate for food. Crab pellets can comprise up to 50%of your fiddler crab’s diet.

Frozen Foods

Frozen foods available for your fiddler crab include plankton, brine shrimp, and bloodworms, items that would be their natural diet. Frozen food should make up 20-30%of your crab’s diet.


Vegetables can be provided as a supplement to pellets and frozen foods to provide extra nutrients. Good vegetables to offer include lettuce and boiled zucchini. 

How Do I Know If My Fiddler Crab Is Healthy?

Health issues are uncommon in fiddler crabs when they receive proper care. When water quality is not kept up, however, it may lead to bacterial or fungus infections, which may cause damage to their shell. Eventually, the infection can affect the crab internally.

Should your crab develop an infection, you can bring it to a veterinarian. However, not many veterinarians have experience treating crabs. For this reason, prevention is always preferred. The aquarium water should be filtered, and a 20% water change should be done every two weeks to prevent fiddler crab diseases.  

Additionally, fiddler crabs molt about every two months. During these times, they may stop eating and become more lethargic. When they complete their molt, they should return to normal activity.

Breeding Fiddler Crabs

Because of their elaborate breeding habits, it’s impossible to breed fiddler crabs in captivity. While the fiddler crabs live in brackish water in the wild, they move to the ocean to lay their eggs. The eggs then hatch into larvae, who become part of the free-floating plankton of the open ocean. 

When the larva matures, it’ll go to the coastal, brackish waters where adult fiddler crabs make their home. Duplicating these conditions has yet to be accomplished in captivity.  Though breeding isn’t possible in captivity, you may be able to observe mating behaviors.

Male fiddler crabs will court females by constructing sand nests and waving their enlarged claws. You may even be fortunate enough to have the female lay eggs, but no home aquarist has yet been successful in hatching them. Recently though, the Burgers’ Zoo biologists did manage to achieve this feat! 

Are Fiddler Crabs Right for Your Aquarium?

Fiddler crabs are a good addition to the aquarium hobby with their easy-care requirements and engaging nature. The most important thing is to get the water quality right. If you get this right, everything else should fall into place. We would enjoy hearing your comments if you have fiddler crabs and please don’t forget to share this article with your aquarist friends.

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