You’ve probably seen and heard of the Hermit Crab (Superfamily Paguroidea) before. Ever wondered why these crabs are called hermits? There’s a clue in the name.
These decapods (two claws and four pairs of legs) have fragile exoskeletons, unlike most other crabs.
So what is a softer-shelled crab to do? They borrow the used shells of other mollusks to protect themselves. Basically, they don’t create their own shell home. They are little nomads who search out and use others’ discarded protection systems so they can get some defense for predators.
They can be found in marine environments spending most of their time underwater. There are also terrestrial Hermit Crabs which are usually limited to tropical climes and are the more common type to be acquired in the hobby.
It’s a misnomer to say that they are purely terrestrial, though, since they need access to both freshwater and saltwater to survive.
Fascinating creatures, Hermit Crabs have an interesting background and story to tell.
Let’s get under the shell of these interesting creatures found in abundance all over the world in a huge variety of forms.
Hermit Crab Behavior
First things first, it’s important to know that Hermit Crabs should never be kept alone. They are incredibly social creatures who normally pile up together to sleep in the wild.
It’s essential that they have company in your aquarium. But the caveat is that if you overcrowd your tank, there will be infighting. Overpopulating the space can result in your hermit crabs squabbling over their mobile shells, even to the point that one crab might try to extricate a crab from a shell to steal it!
To avoid this hooliganism, you should have spare shells available in the tank for crabs to choose as they see fit.
They will molt their soft outer skin twice a year. When this happens, you should expect it to be less active and see a decrease in food and drink consumption. It takes some time, several weeks, for their soft skin to harden enough for the wider world. They will usually bury themselves for protection, so it’s important not to disturb them during this period as they are extremely vulnerable.
Like other crabs with hard exoskeletons, you should leave the shedded skin in the tank as they will usually get consumed, which is good for your Hermit Crab. It provides a rich source of calcium.
Since after molting, the crab is slightly larger, they seek out a new shell that fits their new proportion. You will need to keep a sequence of larger shells in readiness for their growth spurts. Ideally, have more than a few in the larger size since they are particular about their mobile home choices!
Hermit Crabs are primarily nocturnal creatures, and they will have their most activity during those evening hours.
These crabs live in the wild in coastal areas where they have fresh water readily available. However, weekly they will seek out saltwater in order to bathe. This is why it’s imperative that you provide both types of water for your Hermit Crab so they can do what comes naturally.
Since all crabs are wild-caught, you should ensure you bathe any newcomers to your population to avoid inadvertent intruders like crab mites.
Be aware that they have also often had an arduous journey to get to your supplier, often in less than ideal circumstances. It’s common to get a hermit crab and then have it die quite suddenly after buying it. Until it accomplishes its first molt, you should treat it delicately and not try to get too involved as it settles.
Hermit Crab Lifespan
If you cater to the needs of your Hermit Crab, you could expect them to live for up to 15 years. The quality of their tank conditions will impact their lifespan, as always, so you can expect a longer life if you meet their requirements meticulously.
Unfortunately, too many fail to include the social aspect that they crave and end up seeing them perish after only a few months.
We will discuss more on tank requirements a little later in this article.
Hermit Crab Appearance
Considering that they all acquire random shells, they can have a wide variety of appearances in the hobby.
Their size will depend on the exact species you acquire, but usually, they can reach 2 – 3 inches. Some can reach 6 inches, while juveniles will rarely exceed 0.5 inches.
The most common one caught for captivity is the Purple Pincher (Coenobita Clypeatus) with a large purple pincher claw.
They have large and expressive eyes on stalks, and their legs curl underneath themselves, not unlike when you curl your hand into a fist or make your fingers walk forward on a table.
Hermit Crab Habitat And Tank Requirements
Since these crabs are normally coastal inhabitants, you will need appropriate access to both freshwater and saltwater.
It is not appropriate to use table salt in tap water to create saltwater for your crabs!
Use only approved salt supplies as instructed by your provider.
They also require humid conditions to prevent their gills from drying out, or they will suffocate slowly over months. This is a slow and painful death which many do not realize is happening.
Tank Conditions
Getting a tank ready for Hermits is straightforward but not the same as what is required for a fish tank.
You’ll need a glass tank with a cover and be able to regulate the temperature at around 30ºC and not let it drop below 20ºC.
Start off with a sandy substrate that replicates their natural habitat. Allow that to cover the floor of the aquarium. Keep the sand moist and include items that your crabs can climb as they enjoy exploring and are active little things.
The depth of your substrate should be four times deeper than the crab is in size.
Try using a heater at one end of the tank so your Hermits can self-regulate their temperature at a level that feels comfortable. This will also help provide the 50 – 70% humidity needed from the water bowls.
Some owners provide misters that will add to the humidity levels in more arid climates.
Your crab will access the freshwater for drinking and use the salt water for bathing. Commercially prepared Hermit Crab Salts can be easily obtained and mixed in the appropriate ratio. Ensure that you always use dechlorinated water in both cases.
Solid bowls are ideal for the two water supplies as anything too lightweight will easily tip over with these enthusiastic climbers! You should be changing these waters on a daily basis.
Feel free to add in real or fake plants as areas to hide in, along with driftwood for them to clamber over. Moss often works well to help retain moisture in tanks too.
And don’t forget a lid to prevent any unwanted Great Escapes!
Avoid bright or overbearing lighting conditions; these guys prefer low lighting. It’s usually best to have lighting on a 12-hour cycle.
Tank Size
The minimum tank size for 1 – 4 Hermit Crabs would be a 10 gallon one, and for every additional one, you should add 3 – 5 more gallons.
Crabs can be stressed by overcrowding, though, so don’t push to have too many at once and see how they settle in.
Choosing Tank Mates For Hermit Crabs
Ideally, you should just keep Hermit Crabs amongst themselves.
How To Feed Hermit Crabs
Hermit Crabs are known as omnivores in the animal kingdom.
Normally Hermit Crabs will use their claws to bring substrate to their mouths in the wild.
They do not enjoy eating the same foods over and over, so you’ll need to have a variety of foods on offer, so plan on having an arsenal of foods to hand!
This will require plant matter like veggies, so consider spinach, leafy greens, or peas to supplement their diet. Then mix it up with proteins like frozen or freeze-dried daphnia, bloodworms, shrimp, or tubifex.
Meats are an important source of protein, and you can even include things like chicken, fish. Don’t forget to include sources of calcium and include a few cuttlefish bones into the tank for them to nibble on (usually found in the bird section in pet stores).
Hermit Crabs will happily eat most foods you add to their tank but ensure you include enough variety to keep them eager to feed and avoid boredom.
Ideally, you should feed your crabs once a day and keep varying your food sources to give them an enriched diet.
Common Diseases And Illness
For Hermit Crabs, the most common issues that affect them are things like poisoning and stress.
Both can happen easily without realizing it.
Stress will present as inactiveness, being isolated, and actually leaving their protective shells. This can present as a result of overcrowding, temperatures that aren’t correct for their needs, whether too hot or cold. Other crabs can also bully a member of the tank community, but this is usually a result of too many crabs in the kitchen.
Household products in aerosol formats are often responsible for accidental poisoning of Hermit Crabs. It’s very easy for these things to drift into the area above the ventilated tank. Since Hermit Crabs are small, it doesn’t take much to disrupt their physiology.
Also to note here, if you decide to let your Hermit Crab explore outside of the tank in your home, avoid carpets. They are usually cleaned with chemicals that can quickly be exposed to those little creatures.
While this may sound startling, if Hermit Crabs are poisoned, they may start pulling off affected limbs themselves, drop their shells, or sit in water since they can’t remove the toxins themselves.
Be observant of these behaviors and take extra special care not to have any aerosol or chemical products near your tank.
Breeding Hermit Crabs
Breeding Hermit Crabs is not a realistic proposition.
While it is possible, it’s exceptionally difficult to get live young without a lot of specialist equipment and effort. Best left to the experts in the field!
Are Hermit Crabs The Right Choice For Your Aquarium?
Hermit Crabs make a great alternative pet, but it’s important to understand that they are not the easiest species to care for. A new person to the aquarium hobby may find them tricky to handle.
While they are entertaining, they do have some elaborate needs that need careful and close monitoring.
Many suffer needlessly because they don’t have the right elements available to them or adequate temperatures and humidity levels allowing them to breathe with their gills.
Hermit Crabs are a nice alternative to keeping fish if you want a short break from a true aquarium. But you should ensure that you are able to meet their specific needs as these crabs should live a long life. Sadly most do not.
Consider these diminutively sized crabs if you want to try your hand at something new and are prepared to do the work it takes to give them a happy and healthy lifestyle.
Take a chance on the ultimate Happy Camper who loves to move house and change up their mobile home on a regular basis.
