Setting up Your Fiddler Crab HabitatI find my fiddler crabs do best in a 5-10 gallon tank or larger. Fiddler crabs are very social and can get depressed if housed alone.
My oldest fiddler crab was a male and lived to be almost 4 years old, but the average life expectancy is 3 years. It's best to start with a group of 4 fiddler crabs, 1 male and 3 females. You can add more females to your consortium, but do not add any more males as they will fight. Fighting can leading to injury and death.
Fiddler crabs are frequently housed in improper conditions due to the common misinformation that they are freshwater dwellers. They are actually brackish water dwellers and will die if housed in freshwater for long periods. They need brackish water with a gravity of 1.005-1.010. The salt in the water does not evaporate and will only need to be replaced during water changes. I mark a sharpie line on the side of my tank where the water line is so I know how much water I need to add. If enough water evaporates, and is not replaced, the salinity will become to high and will harm your fiddler crabs.
Sand is the recommended substrate for fiddler crabs as they sift through it for food. Gravel can also break their legs. Put at least 4-5 inches of sand in their tank so the male can burrow. Male fiddler crabs make borrows to live in and mate (but that is a whole different article). In a bigger tank, more sand is preferred. I put big smooth rocks half-way through the tank to make a wall and put sand in one half of the tank. I then make a slope over the rocks. Make sure your sand rises at least 4 inches above the water line so your crab has room to burrow.
Provide your crab with hides both on the land and water sections of its' tank. Make sure the hides have no holes that your crabs can get stuck in, or their legs pinched. I prefer log aquarium hides and coconut hides, but it is a personal preference. You can try a few hides to see which ones your crabs like the best.
I prefer to use fake plastic plants in my crabs tank as they are easy to clean and can not be eaten or dug up by your crab. Provide lots of plants for coverage. Another thing my crabs enjoy are cork logs and bark as well as reptile hammocks.
Keep your fiddler crabs lights on 9-11 hours a day. I have found that a timer makes life a whole lot easier and gives them a more strict day/night schedule.
Keep your fiddler crabs tank between 75 and 85 degrees Fahrenheit. An aquarium heater will work to heat the water and a reptile heat lamp works well to heat the land section of their tank. ZooMed Combo Deep dome mini works well.
Get a screen top and clips to secure the lid down for your fiddler crabs tank as they are major escapees and you don't want a bunch or crabbies running around your house! A top will also keep other animals such as cats out of your tank.
Perform 5% water changes every week using a syphon to remove waste.
Fiddler Crab DietFiddler crabs are omnivores and like a varied diet. Foods I have had experience feeding my crabs and have had best success with are: Fluvle bug bites, Northfin crisps, vegie, and community, freeze dried crickets and river shrimp soaked in water, butternut squash, cucumber, romaine lettuce, Omega one frozen blood worms, Mysis shrimp, brine shrimp, baby brine shrimp, and zucchini. My crabs favorites of this list of favorites were brine shrimp, baby brine shrimp, Northfin vegie, and Fluvle bug bites, but it varies from crab to crab. Make sure you boil any vegetables until soft before feeding.
When feeding my crabs I put their food in a small shallow reptile feeding dish full of their water. It is easier to remove uneaten food and to clean. After 24 hours remove any uneaten food and replace it.
Sprinkle a small amount of reptile calcium powder with d3 on top of their food. Make sure the calcium powder has d3 in it or they cannot absorb the calcium.
Fiddler Crab HealthCommon health issues with fiddler crabs are loss of legs and claws, acting lethargic, and not eating. They are most commonly caused by incorrect care such as fully aquatic tanks, gravel, and non brackish water. They don't have a lot of health issues they can get but can die suddenly without noticeable symptoms if improperly cared for.
If fiddler crabs legs are broken, they can grow them back. Watch them carefully after they molt to make sure the limb is growing normally and there are no defects. Normal growth should look like a tan-brown colored nub that will, eventually, fold out and grow into a leg. When male fiddler crabs loose their major claw, their minor claw will replace the major claw and grow larger. Their former major claws nub will grow a minor claw.