Introduction: Welcome to the wonderful world of keeping fiddler crabs as pets. These cute little critters are very entertaining and fairly easy to take care of. They only grow to be about 2 inches wide, so they don’t need as much room as fish. This care sheet mainly talks about American species of fiddler crabs, but the care for other species would be very similar, if not the same, as listed here.
Fiddler Species: Fiddler crabs (also known as ‘Calling Crabs’) are in the genus Uca. There are over 65 different known species of fiddler crabs. Only 3 of which are native to the United States.
Ã˜ Mud Fiddlers (Uca Pugnax) are very common on the South Carolina coast, but can be found from Massachusetts to Florida. As their name suggests, they prefer a muddy home. They can be identified by the H-shaped depression on their brownish colored backs and the long, thin eyestalks. The front of the shell and eyestalks can be a blue-turquoise color. The big claw is a yellow-orange or yellow-white color and has a row of bumps on the inside. The walking legs are darker brown and banded.
Ã˜ Sand Fiddlers (Uca Pugilator) prefer a sandy beach. The bodies of a sand fiddler are pink-purple, and the inside of the big claw is smooth.
Ã˜ Red-Jointed Fiddlers (Uca Minax) are the largest of the 3 species. If you didn’t guess already, the joints of the big claw are red.
There is a great website with pictures of the many different documented species. www.fiddlercrab.info/uca_species.html
Fiddler Facts: Fiddler crabs are easily distinguished by the overly large front claw (or chelipod) of the male. This claw makes up over half of the males body weight. These large claws are used for a couple of different things. First, they are very formidable weapons. They show off these claws by waving them at intruders, and if the intruder has a smaller claw, he will back away. They also use claw waving to attract females. The bigger the claw, the better attractive they are to the females. The males also stomp their legs and make noise to help attract mates. Maturity is reached around 1 year of age. Mating season happens from June to August. Once a female chooses a male, they will borrow to mate. These burrows can be up to 23 inches deep. The female will stay underground for 14 days to incubate the eggs before releasing them into the ocean. The baby fiddlers will then spend the next 2 weeks floating in the ocean while they go through several stages of development. This is the reason breeding is very hard (if not impossible) to achieve in a tank, so donÂ’t worry about hundreds of babies running around in your tank. Fiddler crabs can live up to 7 years, but the average captive life span is around 1Â½ years.
What You Need
Ã˜ Tank: 10 gallon glass or acrylic tanks are recommended, but as with all animals, the bigger the space, the better. If you only have one or two crabs, a 5 gallon tank can be used. Remember that a 10-gallon can only hold up to 4 crabs. You will also need a solid lid to keep the humidity and heat in.
Ã˜ Substrate: Sand or playsand is the most common used substrate. It replicates the beach and allows the crabs to dig as if they were in the wild. For more underwater tanks, gravel would work, as long as you provide high spots for the crabs to get out of the water.
Ã˜ Hiding Spots & Rocks: Fiddler crabs need places to hide and call their own. Some people use cocohuts on the dry land part of the tank, while others use aquarium plants and rocks. Whatever you choose to use, make sure that the crabs can 1) get out of the water (as they need access to dry land, and 2) completely hide from sight.
Ã˜ Filtration: To prevent stagnant water, you will need to oxygenate it either with a filtration system, and/or a bubbler. Many people use a small filter in the water. This not only helps keep the water clean and aerated, but the crabs often eat the bacteria from the filter. Another option you have is to add an airstone to the water to create a bubbler.
Ã˜ Water De-chlorinator: Crabs in the wild are not subject to chlorine added to tap water. Because of this, you will need to de-chlorinate your water. This is bought anywhere fish supplies are sold. Follow the directions on the bottle.
Ã˜ Aquarium Salt: Fiddler crabs live in brackish (slightly salty) water. In order to accomplish this, you will need to buy aquarium salt from the pet store. Popular brands include Instant Ocean, Doc Wellfish, and Oceanic. Never use table salt, as it has anti-caking agents that can be harmful to your fiddlers.
Ã˜ Optional: I have never witnessed my fiddler eating out of the dish, but rather sifting through the sand for food. I have found it easier just to sprinkle food along the sand. Therefore, food dishes are your choice. Also, you may choose to decorate your tank with plants. Other than providing cover for your crabs to hide in, the only added benefit is to make your tank more appealing. You can use fake aquarium plants, or real plants that can withstand brackish water. There is a great informational website with pictures that identify what live plants can survive brackish water: http://www.wetwebmedia.com/BrackishSubWebIndex/bracplants.htm
How to Choose Your Fiddler
Ã˜ Fiddlers are commonly sold in pet stores as freshwater crabs. Unfortunately, crabs that are kept in freshwater too long will not survive. Try to buy your crabs as close to delivery day as possible. This will give your crab a better chance at survival.
Ã˜ Please set up your tank days before bringing your crabs home.
Ã˜ Fiddlers are happiest in pairs. If you buy females, then make sure there are equal numbers of males and females as females have been know to kill extra crabs. You can just get all males or all females and have an odd number.
Ã˜ Males are territorial, so donÂ’t overcrowd your tank. A 10-gallon tank can hold up to 4 crabs.
Ã˜ Pick out perky and active crabs.
Setting Up Your Tank
Ã˜ Add Substrate: If you are using sand, you will need enough to fill the tank about 3-6 inches. Pile the sand 6-8 inches on one side, sloping down to 1 inch on the water side.
Ã˜ Add Water: Mixing your water in gallon jugs is probably the easiest. Start with adding de-chlorinator to a gallon of water. Then add the salt. There are many opinions as to how much salt should be added to make brackish water, ranging from 1 tsp/gallon up to 2 tbsp/gallon. All resources agree that the salinity should be between 1.01-1.08. If you have a hydrometer, you can be more precise. If you want to be really precise, the pH should be 8.0-8.3 and the Carbonate Hardness should be 150-350 ppm. After the water is prepared, gently add it to the tank until the water is 1-2 inches from the very top of the sand.
Ã˜ Add Filter: The water may be dirty from the sand after pouring it into the tank. You will want to run your filter a couple of days to clear this up before adding your crabs.
Ã˜ Temperature & Humidity: Being tropical creatures, they need a tank temperature of 75-85 F (24-29c) degrees and humidity in the range of 75-85% RH. You may need a heat lamp over your tank to help keep the temperatures up. Mud fiddlers can tolerate a much more varied temperature range, hence their popularity.
Ã˜ Most fiddler crab deaths in captivity are caused by wrong tank conditions (salinity, pH, temp), overcrowding, or just being kept in fresh water too long at the petstore. Keep the tank in optimal conditions.
Ã˜ When refilling your water, do not add more salt water. Salt crystals do not evaporate as quickly as water does. Adding fresh water (de-chlorinated) will return the water to a proper salinity. Every 6 months, you should do a total water change and add new brackish water.
Ã˜ Fiddler crabs are known as the beach cleaners of the world. They eat microscopic organisms, algae, and bacteria from the sand (and the filters). DonÂ’t rely only on this, as a new tank wonÂ’t have any of the above yet for them to eat.
Ã˜ Supplement your crabÂ’s diet with sinking algae tablets, freeze dried shrimp, plankton, bloodworms, seaweed (found in fish shops or oriental food stores), zucchini, and fresh fish and seafood.
Ã˜ Never feed too much food, as it will foul the water.
Fiddler crabs shed their old exoskeleton (exo) about every 8 weeks. This is called molting. Fiddler crabs molt in the water and only take a couple of hours to do it. They do need iodine and calcium for both molting and proper nerve function. Instant Ocean provides both. Once they shed the old exo, they will eat it to reabsorb the calcium that will help harden the new exo. If it is not eaten within a week, you can dispose of it. It does take a few days for the new exo to harden, and until then, your newly molted crab may remain hidden.
Here is an interesting fact: if your crab looses his big claw, it will re-grow on the opposite side during the molt.