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How Many Hermit Crabs Per Gallon? (Quick Answers)

Thinking of getting hermit crabs? Before buying your crab pet, tank and habitat are the first things you should build. No idea about hermit crab tanks? Read the article to get a clear understanding of the tank and habitat setup of hermit crabs.

How many hermit crabs per gallon?

For small size hermit crabs, 5 gallons per crab. But for bigger crabs, 10 gallons per hermit crab will be perfect. Note that they grow very fast and to avoid changing tanks in some months, start with a bigger tank early on. The minimum tank size is 10 gallons but 20 gallons will be better. 

There is a wide variety of opinions about hermit crabs tanks on the internet. According to some people, small hermit crabs need less space. 2 gallons per 1-inch hermit crab is fine.

Well, that’s true for a few months. But when they grow up, you will have to hustle again for a new tank for your hermit crabs. 

So, if you have less space, get fewer hermit crabs. But keep in mind that you must get at least 3-4 hermit crabs. They are highly social animals and need companions to live healthy lives. 

If you have a 20-gallon tank, get 2-3 adults or 4-5 young hermit crabs. 5 gallons will be enough to hold the young crabs for a few years. 

After that, you will have to remove some of them or get a bigger tank. If you want a permanent tank, straight go for 8-10 gallons per hermit crab.

We recommend getting a medium-size tank as a beginner. Get fewer hermit crabs at first and add more if you enjoy keeping them. 

Here are two types of hermit crabs tank requirements. 

Land hermit crabs:

Land hermit crabs are different from marine hermit crabs. You can keep 2 medium-size land hermit crabs in every five gallons. 

If you are going for land hermit crabs, you should take a long-term plan as they can live up to 20 years in captivity. Marine hermit crabs live 2-4 years and grow a lot faster.

For land hermit crabs, proper space is important, but there are lots of other things you must do right. The temperature, moisture, and substrate play a key role in their health and happiness.

Dwarf hermit crabs:

1 dwarf hermit crabs need about 3 gallons of water. Dwarf hermit crabs are small and omnivorous scavengers. They are among the most beautiful marine hermit crab species and grow about 1 inch.

Because of their small size, they can be fitted in smaller tanks. But look after their food and nutrition. They can start cannibalism if they lack nutrients.

How many hermit crabs in a:

There are different species of hermit crabs and they vary in size. But most of the hermit crabs grow ½ inch to 4 inches. Here is a hermit crab-keeping guide for every tank size.

5-gallon tank:

5 gallons is very small for any kind of hermit crab. But if you have no more options, keep a maximum of 2-3 small hermit crabs. But they will need to be shifted in bigger tanks as they grow up.

Why is a 5-gallon tank bad? Well, in a hermit crab tank, the substrate is an essential thing. One will have to put 4 times of substrate for their shedding. 

The biggest problem of a 5-gallon tank is the space becomes narrower after adding substrate hiding spots, etc.

10-gallon tank:

In a 10 gallon tank, you can keep 4 medium sizes or 6 small-size hermit crabs for their proper growth. 

If you keep more hermit crabs than the ideal number, make sure they have enough places to hide and things to do until you prepare a bigger tank for them.

20-gallon tank:

20-gallon tanks are best for beginner hermit crab keepers. Keeping 2-3 adult hermit crabs is best for 20-gallon tanks. It’s possible to keep 4-5 mid-size and 7-8 small-size hermit crabs in a 20-gallon tank. 

We will recommend 5 hermit crabs of small to medium sizes. Keeping different sizes of crabs is important as the same size hermit crabs will fight for the shells.

30-gallon tank:

3-4 adult-size hermit crabs can live comfortably in a 30-gallon tank. 30-gallon tanks are suitable for 6-7 medium size and 8-9 tiny size hermit crabs. 

Most marine hermit crabs are sensitive to nitrate, so provide fresh saltwater for their longevity. 

40-gallon tank:

4-6 adult hermit crabs can live happily in a 40-gallon tank. 8-9 mid-size and 12 small-sized hermit crabs can live in a 40-gallon tank. 

55-gallon tank:

55-gallon tanks can be a good habitat for 6-8 adult-sized hermit crabs. The bigger tank and population, the more happy your crabs will be. 14 to 15 mid-size or about 20 small-sized hermit crabs can be kept in a 55-gallon tank.

75-gallon tank:

The 75-gallon tank can hold about 10-12 adult hermit crabs. Around 17-18 mid-size or about 30 small hermit crabs can live in a 75-gallon tank.

What is the best size tank for a hermit crab?

The tank size for hermit crabs depends on the species, how much space you have, and how much time you have for your hermit crabs. 

Moisture is an important factor for land hermit crabs. You will have to spend a fair bit of time to keep the moisture right while marine hermit crabs need water change and tank maintenance. 

So, if you don’t have much time for crab keeping, don’t go for a big tank. At least 3 hermit crabs should be kept while a group of 5-7 crabs will keep them happy. 

Depending on less time and care requirements and crab comfort, here is a guide for the tank size of hermit crabs of different species. 

Halloween hermit crab:

Halloween hermit crab can grow 2 inches maximum and needs 10 gallons of water for each crab. So, a 50-gallon tank will be needed for them if you want to keep 5 adult ones. 

But that’s too big to maintain in a short time. So, if you want to make your tank smaller, get a 30-gallon tank and keep 2 medium, 2 small, and one big hermit crab. 

Blue leg hermit crab:

Blue leg hermit crabs are relatively easier to keep and need less space. They can grow ¾ inch and are very popular for home aquariums. 

6-7 blue leg hermit crabs can live comfortably in a 20-gallon tank.

Strawberry hermit crab:

Strawberry hermit crab can grow about 3 inches in size. So, to keep 4-5 strawberry hermit crabs, a 40-gallon tank is necessary. 

Strawberry hermit crabs are land hermit crabs and not picky eaters.

Staghorn hermit crab:

Staghorn hermit crabs can grow about 2 inches in size and a 25-30 gallon tank is the minimum size for them. A 40-gallon tank will be best for staghorn hermit crabs.

How big do hermit crabs get?

Hermit crabs grow ½ inch to 4 inches depending on the species. If you keep proper care of them from a young age they can grow about 6 inches and live more than 10 years.

The banded hermit crab is the smallest (½ in) and coconut crabs are the biggest hermit crabs.

How quickly do hermit crabs grow?

Generally, hermit crabs need 2 years to reach adult size. Small hermit crabs need around one year to reach adult size. 

So, if you are keeping too many young hermit crabs, you will have to set a larger tank within one year. They grow faster in the first years of their life.

What is the best hermit crab habitat?

Hermit crabs are easy to keep but they have some basic habitat requirements. They need to dig in the sand to shade, moisture to stay healthy, and a hiding place to sleep. Check out the tips about hermit crab habitat.

Add sand: 

Add sand as a substrate about 8 inches, so that hermit crabs can dig the sand to shade skin.

High moisture: 

High moisture in the tank substrate is essential for land hermit crabs. Sand is not so good to keep the moisture. Use some coconut fiber with the sand to fix that.

How can you know if the substrate has enough moisture? Easy, try to make a sandcastle with it. If you can’t, you need to apply more water.

72 to 70° F temperature: 

For marine hermit crabs, 72 to 70° F temperature is needed. Land hermit crabs’ temperature requirements can vary depending on the species. 

Proper oxygenation and biological filters:

Marine hermit crabs are sensitive to chlorine and ammonia. Make sure to set proper oxygenation and biological filters. 

Final thoughts

A hermit crab species that grows 2 inches or more, needs 10-gallon space per crab. You can put one or two more than this equation in a bigger tank. Smaller hermit crabs can live in smaller tanks but keep an eye on their growth and provide enough hiding spots for them.