Hermit Crab Enclosure Size - How Many Hermit Crabs Can Live in 10, 20, 30, 40 Gallon Tank

Hermit Crab Tank Size Requirements, Minimum Enclosure Sizes

If you are thinking of getting a pet hermit crab, you must remember that they are social animals and need companions. So can you get only one hermit crab, or do you need to get a few hermit crabs and put them in a tank together? In this post, you will find out how many hermit crabs you should ideally get, hermit crab tank size requirements, and how many gallons each of them needs to live happily. You will discover how many hermit crabs you can house in 5, 10, 20, 30, 40, 50, 79, 90-gallon tanks.

You must never get only one hermit crab. Hermit crabs are social animals and will get lonely and sick alone, so consider getting at least 3 or more hermit crabs so they can live together in one tank.

When getting hermit crabs, make sure they differ in size. That’s because if they are the same size, they will fight over the same shells. If you get different-sized hermit crabs, their shell sizes will also be different. But luckily, most hermit crabs of different species can live well together without fighting.

Read below for hermit crab tank size and minimum requirements.

What is the minimum tank size for hermit crabs?

The minimum tank size for hermit crabs to begin with is 10 gallons, and 20 inches (51cm) long, 10-12 inches (25-30 cm) wide and high. However, a 20 gallon tank is preferred to provide hermit crabs with more space. You will also need at least a 20 gallon tank if you are going to keep bigger hermit crabs. Most young hermit crabs are around 0.5 inches (1.27 cm) in size, reaching 1″ (2.54 cm) in a few years, and around 2-3″ (5-8 cm) in around 5 years.

Please remember that hermit crabs will grow, so they will need more space. It’s best to leave extra room by getting fewer crabs to start with, or expanding the tank later. And possibly, adding more hermit crabs if you enjoy keeping them.

In general, each small crab that is 1 inch (2.54 cm) wide (across the shell) will need 2 gallons to itself. So, you can house five hermit crabs that are 1 inch wide in a 10 gallon tank. If your hermit crabs are bigger, so example 2 inches (5 cm), then they will need around 3-4 gallons each to roam freely. The best thing to do with bigger hermit crabs is to invest in a 20-30 gallon tank to give them more space to roam.

If you are not sure whether you want many hermit crabs, you can get at least 2 small 1″ hermit crabs to start with a 5 gallon tank. However, please upgrade to a 10 gallon tank even if you have only 2 hermit crabs as they need more space. Lack of roaming space will seriously affect your hermit crabs’ well-being, leading to them becoming sick and weak. If starting with jumbo hermits, get a 20 gallon tank straight away.

Please note that hermit crabs start reaching their adult size in 5 to 10-15 years. You must always get a big tank for your hermit crabs once they get bigger in size. A 65-90 gallon tank is necessary for adult hermit crabs.

How many hermit crabs can live in a 10 gallon tank?

How Many Hermit Crabs Can You House in a 5, 10, 20, 30, 40, 50, 75, 90 Gallon Tanks - Guide

A 10 gallon tank is often the smallest tank that you should get if you plan on keeping hermit crabs. Anything smaller than 10 gallons will not provide adequate space for your hermit crab pets. Please note, that 10 gallons will only be a starter tank, and you should upgrade later.

But ideally, you should get a tank that is at least 20 gallons. This will provide your hermit crabs with enough space to roam and keep busy and happy. Hermit crabs are adventurous, and love foraging and traveling long distances in the wild. Of course, if you have less space in your room/home, you can choose a minimum 10 gallon tank and home fewer hermit crabs in it.

You can house around 4 hermit crabs that are 1-inch wide or less (across their shell opening) in a 10 gallon tank. If your hermit crabs are 2 inches wide, you should only house around 2-3 hermit crabs in a 10 gallon tank. In general, allow 2 gallons per additional 1 inch of the hermit crab size. Jumbo hermit crabs need more space, so start out with at least a 20 gallon tank.

How many hermit crabs can live in a 20 gallon tank?

If your hermit crabs are 1 inch (2.54 cm) wide across the shell opening, you can house up to 7 hermit crabs in a 20 gallon tank. However, it’s a better idea to leave an extra gallon for each hermit crab, as it will need more space as time goes on. If your hermit crabs are bigger (2″/5cm or bigger), allow 2-3 gallons per crab.

If you want more hermit crabs and plan on upgrading in the future, you can house more hermit crabs in a 20 gallon tank. In general, more space = the better for your hermit crabs’ well-being. Also, make sure that the tank is not round or in a shape that’s not rectangular (round aquaria are not suitable).

How many hermit crabs can live in a 5, 30, 40, 50, 79, 90 gallon tank?

A 5 gallon tank is too small for hermit crabs. But if you are just starting out and will upgrade as soon as possible, you can temporarily house 2 hermit crabs in a 5 gallon tank.

You can house around 10-12 hermit crabs in a 30-gallon tank. However, the more space for each hermit crab = the better. In a 40-gallon tank, up can house up to 13 hermit crabs. And in a 50 gallon tank, you can house up to 16 hermit crabs. In a 79 gallon tank, you can house around 25 hermit crabs. And in a 90 gallon tank, you can house around 30 hermit crabs.

This is calculated by allowing around 3 gallons per hermit crab. However, this will differ depending on your hermit crabs’ size – allow 3 gallons per hermit crab + an extra gallon per 1 inch of the crab. You will also need extra hides, bowls, logs more hermit crabs you have, so consider that as well.

Hermit crab tank requirements

Hermit Crab Tank Size Requirements and Sizing

Hermit crab tank size and material

The good news is, hermit crabs don’t require fancy tanks to be happy, but you need to keep some important requirements in mind. Make sure to set up hermit crab’s tank before you bring them home. A minimum 10 gallon tank like this one, or a 20 gallon tank, will be great.

Glass tanks will work the best, as hermit crabs require warm and humid environments. A plastic tank like this can work, but you might have issues with keeping humidity high. As many as 50-75 gallons are ideal, and crucial for adult hermit crabs. Keep the tank away from draughts, direct sunlight or air conditioning. Because they are active at night, it’s best to keep them in a living room or similar (so they don’t interrupt your sleep).

A lid with a mesh or vent area for air exchange

Make sure to get a lid that will go on top of the tank, because hermit crabs need a humid environment. However, make sure there’s a small gap for air exchange (if there’s no vent on the lid itself). Hermit crabs are good escape artists, so a lid is crucial for this reason too. Land hermits don’t need to live in water – they live on land. So please don’t fill the tank with water.


Hermit crabs love and need to dig quite deep. Hermit crabs spend most of their time walking, digging and burrowing. They also need to be able to dig and bury themselves in order to molt successfully. Your hermit crab will burrow and stay under substrate until they have molted fully.

Smaller hermit crabs will be happy with around 5 inches (12.7 cm) of the substrate. In general, make sure the depth of substrate is 3 times greater than the size of the crab. Bigger hermit crabs will need the substrate to be around 8-10 inches (20-25 cm) deep. Keep the substrate moist, so that it keeps its shape.

The best mix is around 5 parts of sand and 1 part of coco fiber. You can make your own mix, or get a ready mix like this. Make sure to keep the substrate moist, but it must keep its shape and not be too wet or drip. Make sure it’s deep enough as well.

Even though sand is the most popular choice, there are other substrate types that you can use for hermit crabs. For example, cork bark and mulch are safe woods for hermit crabs. You will find those for reptiles that need higher humidity levels. To clean it, you will need to use a scoop to remove waste. You will also need to replace it fully once in around 4 months.

However, cork bark can be hard for hermit crabs to burrow in, so try to avoid using it on its own. Coconut husk can be better to add texture in a sand/coco fiber mixture, but also allow proper burrowing. Also, avoid using gravel for hermit crabs’ substrate – gravel can be too coarse and scratch their bodies when trying to dig. Hermit crabs are also unlikely to molt with gravel in the tank as a substrate.

Heating, temperatures and humidity

Hermit crabs need warm and humid environments to stay healthy and happy. Ideal temperatures for hermit crabs are 80-82 degrees F (26.6-27.7 C) and humidity – 75-80%. The minimum temperatures for hermit crabs are 75 F (23.8 C), and maximum – 85 F (29.4 C). At night, temperature drops are allowed, unless they get below 75 F (23.8 C). Night-time heating will then be necessary.

To provide heating for your hermit crabs, you can use an under tank heater, or a heating bulb. An under tank heater isn’t a good option, so try to avoid it. The problem is, under tank heaters that go under the tank don’t heat the tank at all. If you place it inside, it will heat the substrate and not the air. Your hermit crabs can also burn themselves when burying.

You should use a lamp (on the outside) – this will be around 25 watts for a 10 gallon tank, and higher for bigger tanks. For lamps, you can use incandescent, LED, fluorescent (compact fluorescent) or even a ceramic bulb/infrared bulbs. UVB exposure is also important. Ceramic bulbs will not produce any visible light, so can be used for general heating.

If visible light is produced, make sure to have bulbs on timers (can be mechanical or digital like this. That’s because it should be dark in the hermit crabs’ tank at night. But if your room is warm and lit up during the day, there’s no need to use any lighting or heating.

You will need to monitor temperatures by placing one to few thermometers inside the tank. You can also get thermometers with a probe like this. It’s always a good idea to cover the probe or keep it away from where hermit crabs can see them, because they will chew on them.

What is more, you will need a hygrometer to check the humidity levels in the tank. If placing a thermometer inside, place it far away from the aquarium floor to see overall tank temperature. To keep humidity levels stable in the tank, you can use sea sponges like this for the hermit crabs. Wet them and place them on their water dish.

To summarize, these are the main basic requirements for hermit crab tank:

  • A minimum 10 gallon tank that can house a few hermit crabs, like this one. But more space = the better. Glass tanks are the best, plastic tanks might work. Avoid fully metal wire tanks or ones without a lid. If your area is very humid, it might work.
  • Lid for the tank (to preserve humidity & heat), that’s mostly solid, with a small vented or mesh area for proper air exchange
  • Substrate to dig and burrow.
  • Heat source – hermit crabs need a warm environment. Depending on needs, get a bulb + UVB source, with a thermostat (to control temperatures) to keep your crabs warm. Can also use a heating bulb with a timer (digital/mechanical). There are many choices for light bulbs.
  • Thermometer and humidity gauge (hygrometer) like this are must haves to check temperatures and humidity levels in the tank.
Hermit Crab Cage Size, Requirements and Setup Tips
  • Sea sponges for drinking water and keeping humidity levels up
  • Climbing accessories and wood pieces
  • Water conditioner (to remove chlorine)
  • Food and water bowls, hides (caves, logs etc.), plants (plastic, silk)
  • Bathing bowl – fill with seawater (you will need hermit crab salt like this, to mix with water).
  • Shells for crabs – around 4-5 shells per hermit crab is crucial. Only choose natural/polished shells that are a bit bigger in size than the current shell your hermit is wearing. Avoid getting glazed or painted shells to avoid any adverse health effects.

Thank you for reading this post on hermit crab tank size requirement and setup tips. If you would like to learn all about lighting and heating for your hermit crabs’ tank, choosing the most suitable bulbs and more – please see this detailed post.