Tank Setup for Hermit Crabs

Hermit crabs make interesting pets when cared for properly. These little crabs are active and when given everything they need, they can have long lives as well. Unfortunately, most pet stores sell them as easy to care for, shelf pets. While they are easy pets in some ways, they do have very specific needs that must be met to ensure their survival.

In this article, I will talk about the tank setup for the Hermit crabs. So that we could give them the best life possible. After all, this is our responsibility as their owners. Even the most basic of Hermit crabitats require the same essential things. These include:

• Space (Tank size)
• Substrate
• Temperature and Lighting
• Humidity
• A water source
• A food bowl
• Toys
• Shell shop
• Cleanup crew

I would like to start off by saying that Hermit crabs are very delicate creatures, sensitive to stress and are susceptible to small changes in their environment. According to the study, signs of stress in Hermit crabs include loss of appetite, decreased activity, leg autotomy, rejected shells also called naked crabs and increased startle recovery time.

Considering the fact they can live up to 30 years (even more), it will be in our interests to give them everything they need!

Without ado let’s start.

1. Choose a Suitable Enclosure for Your Hermit Crabs

How many gallons does a Hermit crab need? What size tank do I need? Well, these are one of the most asked questions. Therefore, let me elaborate here a little bit. Determining how big of a tank to use depends on two things: how big your crabs are and how many you plan to have.

In general, if you are starting with only a few (2 – 3) small Hermit crabs (By the way, you should never keep just 1 crab) a 10-gallon tank will provide them with enough space. However, they will happily live in a larger one. The more space, the better! Note: Be sure that you know which species of Hermit crabs you have and how fast you should expect them to grow.

• Micro Hermit Crabs (Baby Hermit crabs)

These crabs are defined as being less than 2.5 cm (1 inch) in diameter, including legs. Hermit crabs at this size need a minimum tank size of 5-gallons (20 liters). A 5 gallon tank can house around 3 – 4 micro crabs. Each micro crab needs at least 1 gallon (~5 liters) of “private” space, so keep this in mind if you plan to house a larger colony.

Important: The problem of 5-gallon tank is that it will be hard to install everything they need in such limited space. Just keep reading and you will see it yourself.

• Small Hermit Crabs

Small hermit crabs are 2.5 – 5 cm (~1 inch - 2 inches) in diameter including their legs. Small crabs need a minimum tank size of 10 gallons. A 10-gallon tank can technically hold 3 – 4 small crabs, but a more appropriate number would be 2, or 3 crabs. Crowded living quarters are unhealthy.

• Medium Hermit Crabs

The term medium includes Hermit crabs ranging in size from 5 – 8 cm (~2 inches – 3 inches) in diameter, including legs. A minimum of 5 – 7 gallons of “private” space is needed per medium crab. Therefore, the absolute minimum tank size for a pair of medium hermit crabs is a 10-gallon tank. Thus, a 20-gallon tank would be a better choice for crabs at this size.

• Large Hermit Crabs

Large hermit crabs include all crabs over 8 cm (~3 inches) in diameter. These guys need the most space of all, at 15 gallons of space per individual. At this size, a pair of crabs will need at least a 30-gallon habitat. 50-gallon tanks with a minimum width of 18 inches are a better choice, though. Note: The tank should be plastic, or glass with a glass top, to hold in humidity. If your tank has a screen top, you can lay a piece of glass, plastic or even cardboard (as long as you keep heat sources and lamps away from it) over the screen.

2. Add Substrate into Hermit Crabitat

Hermit crabs are land crabs and as such, they need to burrow. Hermit crabs use their burrows, or tunnels for hiding, and molting. There are multiple substrates available. But, the most popular and arguably the best ones are regular Play sand (The clean sand sold at hardware stores for children's sand boxes), or a mixture of 5 parts sand to 1 part Coconut fiber. Coconut fiber enhances the substrates ability to retain moisture and contribute to humidity levels.

Note: Actually, people argue about the best substrate for the Hermit crabs all the time. Some of them, keep crabs in sand or coconut fiber only substrate and claim that they do not have problems for years. Personally, I tend to side with those who are using a mixture (5:1). The point is that sand lacks humidity and dries out pretty fast. So, it can be hard to maintain sand castle consistency. Coconut only substrate gets moldy, prone to bacterial blooms and floods.

Substrate options (check the price to Amazon):

• Zoo Med Hermit Crab Sand,
• Zoo Med Eco Earth Loose Coconut Fiber Substrate,
• Carib sea sand,
• Hermit beach,
• Play sand, etc.
• If you are on the budget, check out the Plantation soil.

Warning: Do not use calcium sand or thermal sand into a Hermit crab tank. The problem is that humidity causes the calcium sand grains to bind (turning in a concrete like mixture inside your crab). As a result, they cannot move or molt properly. Their gills are clogged up and eventually, crabs die.

So, how Deep Should Hermit Crabs Substrate Be?

The substrate in your crabitat should be deep enough to accommodate your Hermit crab's need to burrow. The absolute minimum depth needed varies between crab sizes.

Absolute Minimum Substrate Depth for the Hermit Crabs:

Micro Crabs – 3 or 4 inches (8 – 10 cm) of substrate

Small Crabs – 5 or 6 inches (12 – 15 cm) of substrate

Medium Crabs - 8 or 10 inches (20 – 25 cm) of substrate

Large Crabs - 10 or 12 inches (25 – 30 cm) of substrate

The rule of thumb is that the depth of the substrate should be at least three times deeper than the biggest crab.

Note: Ideally, you should not have less than 6 inches (15 cm) substrate even for the smallest Hermit crab. If the tank size allows, 6 inches should be your starting point for any crab.

Tip: When you prepare Hermit crabitat, always make your substrate an inch or two (2.5 – 5 cm) deeper than you actually want it to be. The reason is that your Hermit crabs will quickly pack it down.

Substrate Consistency for Hermit Crabs

This is another important thing to know. The substrate should be moistened to sand castle consistency at all times. What it means is that you actually want to be able to make a sand castle with your substrate! If your substrate is the right consistency it should hold its shape.

You do not want your substrate to be dripping wet but you also do not want it to be too dry. If the substrate is too wet, mold, mildew, and bacteria will begin to grow which can harm your Hermit crabs, especially when they molt. If it is too dry, your crabs will be unable to dig and their tunnels will collapse and trap them below the surface.

Tip: The first time you wet the substrate, dechlorinated saltwater (NEVER use table salt) should be used. After this only dechlorinated freshwater should be used when maintaining the consistency of your substrate. Salt does not evaporate and can build up over time, reaching deadly levels.

Therefore, if your substrate is too wet, all you have to do is to add more dry substrate to help absorb some of the water. If your substrate is too dry, you need to add some water. Keep in mind that any water ever used for your Hermit crabs should be dechlorinated. Chlorine is very dangerous for them.

Important: Do not do anything with your substrate when your Hermit crabs are molding. It can potentially kill them.

Tip: You can test the consistency of the substrate with a pencil. Stick it all the way down and pull back up. If the tunnel does not collapse, your substrate is fine.

Tip # 2: Do not ever use gravel as a substrate for Hermit crabs. First of all, it is unsafe, they can break the tips of their legs. Second, it will prevent them from molting. As a result, they will die.

3. Heating and Lighting

Ideally, Hermit crabs need an enclosure that offers them a hot side and a cold side. This allows your crabs to regulate their body temperature to their needs. This temperature gradient should range from the lower end of their temp needs on the cool side to the upper end on the warm side. This gradient can be created using an Under the tank heater (UTH), or a heat lamp designed to imitate the sun.

Neither of these is better than the other and which you should choose depends on your individual set up. For small crabitats, a UTH may be best. In contrast, for those with exceptionally deep substrate, a heat lamp may be better.

You will figure out what method works the best as you track your crabitat temperatures and humidity levels. Always keep a thermometer on both sides of the crabitat and never guess, inaccurate temperature readings could lead to you cooking, or freezing your crabs.

• Under Tank Heaters

These heat mats are designed to be placed under the crabitat, or in some cases to the back of the crabitat. Be sure to choose a UTH that is the proper size for your crabitat. One that is too small will not provide adequate heat, while one that is too large may overheat your crabs.

Substrate often holds heat in, so if you have a deep layer of substrate you may find that your Ground level is too cold. This means that your crabs will want to stay burrowed in the substrate, closer to the heat and you won't see them often. In these instances, a heat lamp may be a better choice.

In addition, if you have an average depth of the substrate, there is a chance that it can overheat your substrate and burn or kill molting crabs there. Therefore, the best option can be to put the heater to the side of the tank (not under).

One of the most popular heaters - Zoo Med Repti Therm Under Tank Heate (check the price on Amazon)

• Heat Lamps

Heat lamps come in various types, some provide white light that imitates daylight, others provide red, or blue light, also known as invisible light that imitates night time, or only supply heat.

Your crabs do not need white bulbs, as long as they are in a room that is lit, or that receives natural light during the day. Blue or red lights provide heat without being unnecessarily bright. This light is virtually invisible to your crabs.

When choosing a bulb for your crabs, remember to never use party lights like black lights, or strobe lights that can harm your crabs and cause them eye damage.

• UVB Lighting

UVB lighting is normally used with reptiles, who cannot create their own vitamin D and require it to be able to molt, digest food and stay healthy. Until recently Hermit crabs were not given supplemental lighting. Your Hermit crab can survive just fine without UVB being supplemented, although keepers who have implemented this into their hermit crab care have reported more active crabs, with brighter colors. The decision to use, or not to use UVB lighting is up to you.

Glass and screen filter out up to 90% of the beneficial UVB rays, this is true of both UVB lights and the sun itself, so keep this in mind if you choose to supplement UVB. The most efficient way to use these bulbs is with nothing between the crabs and the light, except air. However, this can be difficult to achieve in a way that keeps the bulb a safe distance from the crabs, so they do not get burnt.

4. Humidity

Humidity is essential to the survival of your Hermit crabs. It should never be less than 75%. Optimal Humidity level for Hermit crab is 80 – 85%. Humidity levels should be monitored with a hygrometer. This gauge should be placed close to where your crabs spend most of their time, in order to accurately display their actual humidity level. A gradient of humidity is normal, as it will be naturally lower near heat sources and on the cooler side of the tank.

Lots of time you can see people using misting to increase the humidity level. Well, DO NOT do that like ever! Misting a Hermit crab enclosure is not at all recommended because of the flooding potential!

Keeping the substrate moist, providing water for your crabs and using a glass top. If your humidity levels stay too high or too low, it can be remedied by adding more moisture, less ventilation or by adding more ventilation. This is normally a trial and error process, so expect it to take some adjusting to get it perfect.

Humidity and Thermometer (links to Amazon):

• Zoo Med™Reptile Terrarium Digital Thermometer,
• Zoo Med Labs Digital Thermometer Humidity Gauge,
• AcuRite 00613 Indoor Thermometer & Hygrometer with Humidity Gauge

Tip to increase humidity in Hermit crabitat.

1. If it is possible for the setup, you can add an airstone in the pools. They will increase the humidity.
2. Build a moss pit. You will need a plastic shower caddy with suction cups, dechlorinated freshwater and Terrarium Moss (link to check the price on Amazon). Soak the moss in dechlorinated freshwater for 3 – 5 minutes. Next, squeeze the water out. Add it in the shower caddy. This is it. The good thing is that it is very easy to maintain. When the moss gets dry, pick it out and re-soak.

5. Water and Food Bowls

Your Hermit crabs need water. Some species are hydrophobic, others may enjoy sitting in their water bowls, but they all need water. There should be two water bowls (pools) in your crabitat. One should be freshwater and the other should be saltwater.

To prepare saltwater, I would recommend using Instant ocean marine salt (check the price on Amazon). This is a great choice. It is pretty cheap and will last very long. You only need about a half cup of Instant ocean marine salt per gallon.

Note: Do not ever use simple aquarium salt, or table salt! Regarding freshwater, ideally, you need to give them something like bottled spring water. Tap water will be the last choice.

Note: When you prepare water for the Hermit crabs, let it age for a day or two. For example, chlorine will usually evaporate out of water within 24 hours. Next, add Searchem Prime. This water conditioner also removes chlorine, chloramine, bind to heavy metals, any ammonia, nitrites or nitrates present for up to 48 hours. Consider Prime as your additional safety net.

Depth and Accessibility of the Bowls

The bowls should be easily accessible and large enough for your crabs to climb into and completely submerge in them. It is very important to provide some kind of ladder (stones, fake plants, etc) to get out of the bowls. Otherwise, they can drown.

Important: This is a very common mistake. People do not provide enough depth. As a result, Hermit crabs cannot get water inside the very back of their shell. They do this by tipping it upward to release air. Therefore, if the shell is not completely under the water, hermit crabs cannot do that.

The terrible fact is that you will not see any negative effects right away. However, over a few years, it will damage their abdomen and eventually kill them. Food bowls are not necessary, but they do make it easier for you crabs to find their food. It also makes it easier for you to keep the crabitat clean.

Tip: Many times you can see sponges in the water dishes. They are supposed to help keep the humidity up in the tank. Unfortunately, the downside is that the sponge becomes a source of all kinds of nasty bacteria, which is not good for the crabs.

Some examples of bowls (links to check the price on Amazon):

• Zoo Med Reptile Rock Corner Water Dish
• Zoo Med Hermit Crab Fruit-Salad All Natural Fruit Treat,
• SunGrow Hermit Crab Feeding Bowl

6. Shells

Do not forget to add in all of your Hermit crabs setups shells. It is really important to provide them with lots of shells. Thus, they can move into that are slightly bigger than the ones they are currently in.

The “Shell shop” should contain shells of different shapes and sizes. It is recommended to have at least 5 shells per Hermit crab, but more is always better. So they have plenty to choose from. Do not give them coned shaped shells, painted shells, and shells with a narrow opening.

Tip: Caribbean Hermit crabs prefer a certain type of shell, called a turbo shell. However, they will sometimes wear other types of shells as well. Hermit Crab Home Turbo Shell (check the price on Amazon).

7. Toys and Decorations

Hermit crabs are very active creatures that enjoy digging, pushing, pulling and climbing. Actually, climbing is their passion. Most of the time you will see them climbing everywhere and exploring everything. The more you give them to explore, the more they will venture out and get active. Supply your Hermit crabs with rocks, decorations, plastic balls, plastic tunnels, crab huts, plastic plants, fish netting, and more. The possibilities are endless.

These are some popular examples for Hermit crabitat (check the price on Amazon):

• Natural Coconut Husk Bird House with Ladder.
• Lizard hammocks.
• Crab Climbing wall.
• Fake plants.
• Saucer hamster wheels (They will love it! Do not use the wire ones. It can damage their legs).
• Cholla wood.
• Natural cork bark.
• Cuttlefish bones (calcium supplement).

The more hiding spots you provide, the happier your crabs will be because they will feel safer. Do not be surprised if your crabs rearrange their crabitat decor frequently. It just means they're happy and playing.

Important tips: Quarantine everything before putting it in the tank. The fastest and simplest way to do that is to boil. Boil all of the décor, shells, wood, toys, nets, etc. You do not want to get any bugs or bacteria. If it is made of plastic you can just dip them and get out. Do not hold it in boiling water, the plastic will melt down.

Warning: Do not give them pine cedar. These are all toxic and dangerous woods to Hermit crabs. They can try to eat it, just to see if it is edible. As a result, after multiple times they got sick and die.

Live Plants vs Fake Plants

Some people say that there is nothing wrong with adding live plants in Hermit crabitat. Of course, live plants are a part of their natural environment. Nonetheless, I do not think that it can be safe to add them. There are several reasons for that:

1. Hermit crabs will try to eat the plant. You will be lucky if they do not get sick.
2. Crabs will climb all other the plants and can break them.
3. Large roots can disrupt their molting space.

Therefore, in my opinion, you should not use live plants in Hermit crabitat. You will not have any problems with fake plants. So fake plants are the best choice.

8. Clean up Crew. Isopods and Hermit Crabitat

Like all living creatures, Hermit crabs produce waste. Eventually, you will have to deal with it somehow.

Like snails in fish or shrimp tanks (you can read more about it in my articles “Benefits of Snails for a Shrimp Aquarium” or “Malaysian Trumpet Snails – Pros and Cons for Shrimp Tank”), Roly polies will do the clean up for you. In the wild, you can find them almost under every rock. The good thing about Hermit crabs as pets, they are usually pretty tolerant of other insects.