Hermit crabs can be land animals, but just 1 in 7 hermit crab genera is terrestrial. Many species live in the ocean, so marine hermit crabs must live underwater when kept as pets.
Hermit crabs and fish live side by side in the sea and can do so in a tank, assuming they’re compatible. That means sharing preferences for water, food, and temperature.
Clownfish, damselfish, gobies, cardinalfish, and wrasses are good tankmates for hermit crabs. However, avoid putting goldfish, betta fish, or cichlids with hermit crabs.
Can Hermit Crabs Live in a Fish Tank?
A fish tank, or aquarium, is considered the ideal home for aquatic hermit crabs.
An aquarium that’s at least 10 gallons in size will provide the following criteria:
- Retain heat
- Enough space for exploration and digging
- Protection from external fumes
- A solid roof to prevent escape
- Easy spot clean and deep clean
To house fish and hermit crabs together, you must adopt marine hermit crabs.
Marine Hermit Crabs vs. Terrestrial Hermit Crabs
As per the Annual Review of Ecology and Systematics, over 800 hermit crab species exist. The Ecuadorian hermit crab is less than half an inch in size, while the coconut crab can grow to over 3 feet.
What matters most is determining whether a hermit crab lives underwater or is land-based.
Marine hermit crabs live in the ocean and can’t breathe for long on land. Terrestrial hermit crabs can breathe on land, with sufficient humidity, but for only 20-30 minutes underwater.
There are 7 recognized families of hermit crabs, and 6 live underwater. Here’s a breakdown:
| Family | Common Species |
| Coenobitidae (Terrestrial) | Ecuadorian, Australian, Blueberry, Coconut, Strawberry, and Caribbean. |
| Diogenidae (Marine) | Scarlet Reef, Eye Spot, Furry, Blue Leg, Whitebanded, Zebra, and Anemone. |
| Paguridae (Marine) | Arcadian, Black-Eyed, Whiteknee, Polka Dot, New Zealand, and Blueband. |
| Parapaguridae (Marine) | Oncopagurus, paragiopagurus, and strobopagurus. Rarely kept as pets. |
| Parapylochelidae (Marine) | New species have been discovered, like the mesoparapylocheles michaeljacksoni. |
| Pylochelidae (Marine) | AKA symmetrical hermit crabs. This family is endangered and unavailable as pets. |
| Pylojacquesidae (Marine) | Pylojacquesia colemani and lemaitreopsis holmi. Unavailable as pets. |
Terrestrial hermit crabs of the coenobitidae family can’t live with fish because they’ll drown.
Coenobitidae hermit crabs have gills but have evolved to live on land. Their lungs breathe oxygen, and they soak in water occasionally to retain water.
Can Hermit Crabs and Fish Live Together?
Hermit crabs enjoy species-specific companionship. In the wild, hermit crabs live in colonies, so avoid leaving one hermit crab alone in a fish tank because it’ll quickly grow stressed.
The best hermit crab breeds to pair with fish include:
- Blue Leg
- Zebra
- Dwarf Red Tip or Yellow Tip
- Polka Dot
- Electric Blue or Electric Orange
In addition, consider the water requirements of fish and aquatic hermit crabs.
Not all exotic fish can survive in saltwater or freshwater. In addition, marine hermit crabs need water temperatures between 72-78 degrees Fahrenheit to flourish.
Will Hermit Crabs Attack Fish?
Hermit crabs are omnivorous, opportunistic scavengers. However, it’s rare for a hermit crab to attack prey. Besides, most hermit crabs suitable for living with fish are smaller than the fish.
So, it’s unlikely that hermit crabs will attack your fish. As we’ll explain, marine hermit crabs prefer to eat algae and plant life, acting as the aquarium’s janitors.
What Are The Advantages of Keeping Fish with Hermit Crabs?
The benefits of combining aquatic hermit crabs and fish include the following:
Decoration
One of the best things about owning an aquarium is its aesthetic splendor.
Sitting and watching a fish tank is relaxing, especially if populated with tropical marine life. Hermit crabs can add even more color and pizzazz to an aquarium.
Offer a selection of brightly-colored shells for the hermit crabs, and they’ll choose whichever shell serves their needs best. Some hermit crabs may even change shells several times per week.
Many species of hermit crab have a striking appearance. For example, the electric blue or electric orange hermit crabs will brighten any aquarium.
Cleaning
Hermit crabs are tireless cleaners of an aquarium. Instead of scavenging carcasses, they eat algae, fungi, fish feces, and their own waste.
Moreover, hermit crabs are drawn to new, novel food sources. As a result, hermit crabs may eat dead fish that sink to the bottom of the tank.
Recreation
Hermit crabs entertain fish and vice versa because they’re curious creatures.
Life can be quite dull in a tank for underwater animals, especially tropical marine life. Fish and hermit crabs are accustomed to swimming free, where they’ll encounter other wildlife.
Pairing these two species will replicate wild living as much as possible.
What Are The Disadvantages of Pairing Fish with Hermit Crabs?
Before introducing hermit crabs to their new home, consider whether you can meet their needs. Hermit crabs bring many new dimensions to a fish tank but create more work.
Dietary Needs
Hermit crabs eat algae and detritus in an aquarium but still need to be fed. The problem is that the dietary needs of hermit crabs may differ from fish.
Hermit crabs enjoy fish flakes as an occasional treat, but you’ll need to research the dietary preferences of hermit crabs and ensure that they aren’t harmful to fish.
Don’t go overboard when feeding hermit crabs because uneaten food will rot and lead to higher ammonia and nitrite levels. Check that food is being eaten and perform regular spot cleaning.
Molting
Molting is the process of shedding an exoskeleton while a new exoskeleton grows. Young hermit crabs undertake this process regularly, and older hermit crabs will molt every 18 months.
While a hermit crab is molting, it’s vulnerable, so ensure hermit crabs can burrow. According to the Journal of Experimental Marine Biology and Ecology, hiding reduces mortality while molting.
If you understand signs that a hermit crab is set to molt, you can move it to another location. In advance of molting, hermit crabs will do the following:
- Become shy and lethargic
- Turn a dull color, usually gray
- Eat more than usual
- Burrow at every opportunity
When a hermit crab molts, it discards its old exoskeleton, which will be eaten.
Space Requirements
Ensure the aquarium is large enough to accommodate fish and hermit crabs.
With fish and hermit crabs alike, more space is better. Never get a tank below 20 gallons in size. The more room you have, the more marine animals will be free to swim and explore their environment.
Sharing a tank with fish provides 4-6 inches of substrate because hermit crabs will look to burrow for solitude and safety. The more substrate, the happier they’ll feel.
Substrate
Hermit crabs need the opportunity to burrow, so rocks and gravel are insufficient. A hermit crab needs something soft, ideally sand.
You can get sand for an aquarian from any pet shop. These will typically be colorful and created with aesthetics in mind. However, play sand will suffice.
You can use sand for a child’s sandpit, which will be safe for hermit crabs and fish.
Fish That Can Live with Hermit Crabs
Not all fish can live with hermit crabs. You must ensure that you weigh up the pros and cons of inter-species living arrangements. Things to consider include the following:
- Water temperature
- Feeding schedules
- Temperament
- Saltwater and freshwater needs
- Chemical levels in the water
- Available tank space
Some fish accompany hermit crabs better than others, so let’s review some possible pairings:
Clownfish
Hermit crabs and clownfish make natural tankmates. Given that these two species co-exist peacefully in the ocean, they can replicate this relationship in captivity.
Clownfish can grow aggressive, such as when they change their gender. Clownfish are born male and can choose to evolve into females to become the dominant female in a school.
Even if this transpires, a clownfish usually leaves a hermit crab alone, as they’re only territorial toward fellow fish. As clownfish and hermit crabs enjoy similar living conditions, they usually get along fine.
Damselfish
Damselfish have a similar temperament to clownfish, which means they get along okay with hermit crabs but may attack other fish.
If you want a hermit crab tank with fish, consider damselfish because this species is tough and hardy.
Just be wary about adding more fish afterward, as they can be dominant and territorial. As with clownfish, a damselfish is unlikely to show any interest in hermit crabs.
Royal Gramma
Royal gramma fish are among the most visually impressive saltwater marine life. Also, they’re as shy and peaceful as hermit crabs, so the two species rarely interact.
The only note of caution is shared seclusion. Royal gramma fish, like hermit crabs, want to hide, so they may invade each other’s territory.
Gobiidae
Colloquially known as “gobies,” the Gobiidae family are often used as tankmates for hermit crabs. Gobies are docile fish and rarely attack hermit crabs.
Gobies and hermit crabs share a love of shells because they like to build and reinforce walls around a den. So, they may come into conflict if a gobie grabs what it thinks is an empty shell and drags it away.
These two species can live together harmoniously. Just ensure there are lots of shells to go around. Allow for 2-3 shells for each fish and hermit crab to minimize any risk of conflict.
Wrasses
Wrasses are bright fish with a reputation for being cantankerous, attacking other fish that look similar. Hermit crabs and wrasses can live side by side without incident, though.
Be mindful of the voracious appetite of the wrasse, as they may attack and eat an exposed hermit crab. Ensure that any hermit crabs aren’t left without shells and that there’s enough substrate to burrow into.
Pajama Cardinalfish
The pajama cardinalfish is a beautiful and docile addition to any aquarium. Multiple pajama cardinalfish will live peacefully together and leave any hermit crabs alone.
You could pair a pajama cardinalfish with any other fish we’ve discussed, but a more dominant species can bully them.
Guppies
Guppies are freshwater fish, but they can tolerate some salt water, which means they can live alongside hermit crabs.
While there are undeniably better choices, guppies are ideal for smaller tanks. The diminutive size of these fish and hermit crabs takes up little space.
Perhaps more importantly, guppies are just as gentle as hermit crabs. Just be wary of larger hermit crabs, as a more aggressive and confident crustacean may attack a curious guppy exploring the substrate.
Cleaner Shrimp
The cleaner shrimp eats algae and debris in an aquarium.
It’s rare for cleaner shrimp and hermit crabs to fight. As long as both animals have hiding places, they’ll get along okay.
Cleaner shrimp will fare better than sea snails, as a hermit crab may attack sea snails to take their shell. Cleaner shrimp have no shell to offer and are fast and agile enough to avoid pincers.
Fish That Shouldn’t Live with Hermit Crabs
While many species of fish peacefully co-exist with hermit crabs, this doesn’t apply to all fish. Some of the most popular pet fish and incompatible with hermit crabs, including:
Goldfish
Goldfish are among America’s most popular aquatic pets, but hermit crabs and goldfish shouldn’t live together. Both species have unique needs.
Goldfish need fresh water, while hermit crabs need salt water. In addition, goldfish prefer to live in cooler water than aquatic hermit crabs.
Betta Fish
Betta fish are among the most popular tropical fish in the world, as they look stunning and bring any aquarium to life. Can hermit crabs live with betta fish? Unfortunately, the answer is usually no.
Consider the other name for bettas – Siamese fighting fish. These aren’t shy and retiring fish, so a betta may attack hermit crabs, so they’ll always feel stressed.
Cichlid
Bettas are shrinking violets compared to cichlids. These brightly-colored fish look amazing but are highly territorial, constantly battling for dominance and territory.
If a cichlid has seen off competition, it’ll quickly turn its attention to hermit crabs. This fish is large enough to attack and eat a hermit crab, so they’re unlikely to survive long with these tankmates.
Marine hermit crabs can live with certain fish, which can be a mutually beneficial arrangement for all involved. Hermit crabs keep a fish tank clean, eat well, and add character to an aquarium.
