Hermit Crab Care Guide

This article is written by Pet Circle veterinarian, Dr Nicole Wynne BSc BVMS MANZCVS (Unusual Pets)

Hermit crabs are cute little critters that provide hours of entertainment as they bustle around their enclosures. Although they are commonly sold as pets, they have specific requirements due to their unique ecological niche. Hermit crabs are crustaceans that live on land, and specifically the transitional zone between sea and land - the beach! They also live in other similar environments like mangroves. Although they live next to the sea, they still have a requirement for fresh water. This ecological niche makes them a very unique part of the ecosystem that helps break down detritus and other organic matter, and also means that they have very specific requirements that need to be met in captivity.

Pet hermit crabs in Australia are a tropical species with the scientific name Coenobita variabilis, and they naturally occur along the northern, tropical coast of Australia. Because of their natural habitat, they require a warm, humid environment that can be difficult to maintain in cooler climates. However, with the right preparation and equipment, you can provide hermit crabs with everything they need to thrive. 

A licence is not needed to purchase and keep hermit crabs, but a collecting licence is required to collect and sell them from the wild. The majority of hermit crabs sold in captivity are captured from the wild, and this is another important reason why they should only be purchased if you are sure you can care for them appropriately. 

Even though they are small and inexpensive, they are not low maintenance pets for children as their husbandry requirements are so specific. They can also live up to 30 years and represent a significant commitment! Hermit crabs also like having friends, so prepare to get more than one.

In this article:
Facts about hermit crabs
Preparing for your hermit crab
Caring for your hermit crab
Further reading

Facts about hermit crabs

Size	Place of origin	Temperament
Small	Australia	Placid
Life expectancy	Length range	Weight range
15-30 years	0.5-3 cm	10-100g
Enclosure size	Activity level	Active period
Medium	MediumÂ	Night

Are hermit crabs good pets?

Hermit crabs are good pets for people that love to watch them interact with their environment and each other. They do not enjoy being handled, and so are not a good choice for people who want to be able to pick up and interact with their pet. They also require a temperature controlled environment, as well as frequent checks on humidity, UV lighting, and water quality, making them unsuitable pets for young children. However, they can be suitable pets for teenagers that are willing to make the commitment. Although they can pinch, they are so small that they cannot cause injury to a human.

Are hermit crabs nocturnal?

Hermit crabs are nocturnal, but also active during the day, which makes them a great option for people who love to watch them scurry around their enclosure. They also are more active during dusk and dawn when the tides change.

What do hermit crabs eat?

Almost everything! They occupy a special niche in the ecosystem and act as the cleanup crew. They scavenge and eat fallen fruit, washed up fish, seaweed, vegetation, and even nuts. They need a varied diet in captivity to stay healthy.

How big do hermit crabs get?

Older individuals can get surprisingly large, up to fist-sized! Young hermit crabs usually are about the size of a bottle cap.

How long do hermit crabs live?

They can live up to 30 years! Sadly, many don’t make it that long due to poor husbandry.

Are hermit crabs aggressive?

They are not aggressive, but will pinch with their claws when they feel threatened. However, many crabs are so small that it does not cause injury.

Preparing for your hermit crabs

Once you’ve decided that hermit crabs are right for you, read on! Preparation is the key to a smooth transition to their new home. First of all, you will need at least 3 days to prepare a new enclosure, so plan ahead. Second, don’t skimp on their enclosure. A more expensive glass tank will far outlast a cheap plastic tank, and it will also make it much easier for you to maintain proper temperature and humidity. It will also save you money in the long run as a quality glass tank is likely to last for decades.

Checklist

Hermit crab enclosures

The enclosure should be large enough for the number of hermit crabs you plan to have, and plan for about 20 litres of tank size per hermit crab. Wide, long tanks are much better than tall tanks. However, depth is also important, and there should be at least 2-3 crab lengths of substrate for them to dig in. Height isn’t as important, but do ensure that your UV light and heat lamp if using can be placed properly without your crabs accessing it. 

Especially if you’re in the cooler states of Australia, insulation may be required in the colder months to help your heating system and thermostat maintain temperature, so do keep an eye on the readings. Bubble wrap and styrofoam are great insulators and can be placed outside the tank walls. 

Glass ticks all the boxes for a quality hermit crab enclosure, and they are also easy to clean and disinfect. While the top of the tank can contain mesh panels, some of the mesh may need to be covered up depending on the humidity readings. 

The tank should also be placed in a quiet room, away from foot traffic or other pets, and without too many temperature fluctuations. As hermit crabs are prey animals, they are shy and will be stressed by too much noise or movement.

Hermit crab heating

A heat pad placed on the sides of the enclosure is the best option to reduce humidity loss, but you may require multiple pads to maintain a temperature between 25-30 degrees Celsius. It is easiest in the long run to set up your heating elements to be controlled by a thermostat, which will automatically read the temperature from its thermometer and adjust the heating elements accordingly. Your tank should have a variety of temperatures available so that your crabs can self regulate their own temperatures. When monitoring temperatures, ensure that your substrate doesn’t get too hot, as overly warm substrates can damage your crabs as they burrow, or at worst, when they are moulting.

Hermit crab lighting

Hermit crabs require a day night cycle of about 12 hours each, and visible light is important for regulation of natural behaviours. They should also have a UV globe that is no more than 30 cm to the ground. Although UV light is important to hermit crabs, never place the tank in direct sunlight, as this will dry out the enclosure and remove important humidity. Red light can be used to view your hermit crabs at night as this will not disturb them.

 

Hermit crab furniture

A hermit crab enclosure should try to mimic the natural environment as much as possible, which is great news as they live in some of the most beautiful places on earth! Hermit crabs live on beaches and the transitional zone between beach and tropical forest. Furniture can include driftwood, rocks, plants (real and fake), hides (small pots, caves, or hollow pieces of wood), and larger shells. Hermit crabs can also clamber up large branches and gentle slopes. A variety of appropriately sized shells should be available for crabs to change into.

Hermit crab substrate

Hermit crabs like a combination of sand and coconut fibers as a substrate, and coconut fiber or coconut coir is a great option for helping maintain humidity in the enclosure. When moistening your substrate, add brackish water until the substrate holds together loosely when clumped in a fist. It is easier to add water than to dry out substrate after it is in the tank, and overly wet substrate can make the enclosure prone to mould or bacterial growth. After putting in the substrate, let the tank sit for 48 hours while monitoring the humidity. If the humidity stabilises at 70-80% after that time period, you’re all set. If it is too low, mist the substrate or add waterlogged moss or sea sponges, then wait another 24 hours and monitor the humidity. 

Hermit crab water

Hermit crabs need access to both salt and fresh water. Do not use table salt or pool salt, and only use salt that is made for marine aquariums, and mix according to package instructions. Have at least one fresh water source, and one salt water source, and you can place them near the heating elements to increase the humidity of the enclosure, just make sure you can top it up frequently! It is important to ensure that your crabs can climb out of the pools easily, as they cannot swim! Use driftwood, rocks, or you can even use aquarium silicone to stick objects to the side of the pool. 

These pools should be changed out and cleaned every 2-3 days to maintain water quality. You can also add water filters and/or bubblers to the pools if they are large enough, but ensure that your crabs can’t reach the wires as they may pinch them!

Ensure that all water you use, even the water you use to make salt water, is treated appropriately prior to using. Tap water should be allowed to sit uncovered for 24 hours to allow chlorine to evaporate, and water conditioners should also be used according to manufacturer recommendations. Some water conditioners will also remove chlorine, and ensure you read the packaging thoroughly. 

You can store treated fresh and salt water in bottles for future use.

Hermit crab diet

Hermit crabs require a variety of foods to stay healthy, and commercial hermit crab food should be used as part of their diet, and not the sole source of nutrition. Although this sounds daunting, you likely already have food suitable for hermit crabs at home. A range of vegetables can be fed, such as broccoli, peas, corn, seaweed, salad greens, and carrot. They can even have coconut, squash, and mushroom! Fruit can also be fed in smaller amounts, like apple, pear, strawberry, blueberry, stonefruit, and melons. Whole grain and nuts are a special treat, and hermit crabs do get those in the wild when they fall from trees! Once in a while, they can also get higher protein foods like egg, fish, and even dried insects like mealworms!

Hermit crabs need calcium in their diet to grow their exoskeleton, so high calcium options like spinach and parsley are great, as well as cuttlebone, eggshell, and crab/prawn shells.

Hermit crab hygiene

Enclosures should be spot cleaned daily, with soiled areas of substrate and uneaten food removed, along with any contaminated substrate or furniture. Standing water should be changed every 2-3 days, and water with filters or bubblers every 3-5 days. The whole enclosure should receive a thorough clean every 2-4 weeks depending on how many crabs you have, where the crabs are moved to a temporary enclosure while the substrate, furniture, water, and food bowls are all removed, cleaned, and replaced. 

Use an aquarium-safe cleaner like F10, and ensure it is wiped or rinsed off before replacing the tank contents. Be careful when moving your crabs!

Caring for your hermit crabs

With all the preparation done, the fun part is caring for and watching your hermit crabs! Keeping up with regular maintenance is the best way to help keep your crabs healthy. Once you introduce your crabs into the new enclosure, let them settle in quietly for the next few days. This will also allow you to observe their normal behaviour and make any minor adjustments you need to make to their enclosure, and especially make sure that they can get in and out of their water pools safely. 

Hermit crab moulting

Hermit crabs need to moult their hard exoskeletons as they can’t grow as the crab grows. Although they live in shells, they also have their own hard skeleton around the soft parts of their bodies. Moulting is an important and dangerous part of a hermit crab’s life, and so it is important to recognize the signs of moulting so you can ensure that everything goes smoothly. As a hermit crab that is moulting has no protection against the outside world, it is easy for them to dry out, get injured, or lose limbs. 

Hermit crabs moult every 12-24 months depending on their growth rate. Many hermit crabs will display particular behaviours when they are about to moult:

However, the biggest sign of an impending moult is your hermit crab digging into the substrate and not emerging until it is finished moulting. Depending on the size of the crab, a moult can last from a week up to a year for very large hermit crabs. If you find that your crab comes out of their burrow, they are not moulting, as burrowing is a normal behaviour. It can also be a stressful time for you, as you cannot see your hermit crab during this period. It is very important that your crab is not disturbed until they emerge on their own, as digging them up or moving them can cause serious problems, even death. 

Hermit crab shells

Part of the fun of keeping hermit crabs is watching them choose new shells! Supply 3-5 spare shells per hermit crab, as they will often try multiple shells before deciding on the best one for them. You can keep all the spare shells in a shallow dish in the enclosure to prevent them from getting buried in the substrate. Provide a variety of shells as hermit crabs tend to have preferences to what they like, and it differs from crab to crab! Some crabs like round entrances, some like D-shaped ones, and crabs even have preferences as to spiral shells, round shells, or elongated shells. They will even modify their shells to suit their needs!

Ensure that any shells you provide are whole and don’t have cracks or holes, as the shell is important to help crabs stay moist. Check all shells for sharp edges or other signs of damage. Natural shells are the best, and you can collect them from areas without naturally occurring hermit crabs, as we don’t want to take homes away from wild crabs! Thoroughly check to ensure these shells are empty before taking them home. To make sure these shells are safe for your crabs, boil them in fresh, treated water for 10 minutes, then allow to cool thoroughly prior to adding them into your enclosure. 

Hermit crabs that don’t have a shell are in distress, so always check your temperature and humidity if you notice a crab out of their home. Ensuring that there are lots of spare shells to go around prevents bullying and shell stealing. If a crab still doesn’t go back into a shell, isolate them in a smaller enclosure with appropriate temperature and humidity with several shell options, and leave them alone in a dark and quiet place. 

Finally, never pull a hermit crab out of their shell. This can cause injury and death, and it is also extremely distressing for the crab, as this only happens when they are about to get eaten. 

Further Reading

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