Creating a Crabitat

Aquarium & Lid

You will need an aquarium that is at least 20 gallons in size, even if you only have one crab (although it's recommended to keep at least two crabs together). You need to increase the size of the tank by 10 gallons per crab. For example, if you have 1 crab, you'll need a 20 gallon tank. For 4 crabs, you'll need at least a 40 gallon tank. This is only a general guideline and the tank size should be increased when housing larger crabs. Jumbo crabs should have 15 gallons of space per crab.
To cut costs, search online for used tanks in your area. Facebook Marketplace and Craigslist are great places to look. The tank does NOT have to hold water, a leaking aquarium is perfectly suitable for a crabitat. Make sure the tank's frame is intact and able to support a lid. The tank and stand pictured above is 130 gallons and was purchased for $180 off of Craigslist. We purchased some paint that complimented the existing mosaic and dressed it up a bit.
The lid must be able to keep in the humidity and prevent escape. Mesh lids typically used for reptile enclosures are NOT acceptable, they will not retain the humidity. If your tank has a mesh lid, you can lay a piece of plexiglass, coroplast, or similar solid material across the top. Plexiglass can be purchased at Lowes or Home Depot and they will cut it to size for free. Coroplast is white plastic that resembles corrugated cardboard, is inexpensive, and available at many hobby/craft stores and some home improvement stores. It is often used for making signs.
Crabs are stronger than they appear and are crafty escape artists. If the lid does not have a latching mechanism, place something heavy on top to keep them from lifting it up and crawling out.
Do not worry about the ventilation, even with the solid lid, adequate air exchange will occur each time you open the lid to clean out their pools and feed them. There may be a need to add holes in the lid to vent the humidity. Some tanks just seem to stay more humid and having a few vent holes can manage the issue. If you determine that your tank needs ventilation holes, you can drill them yourself but add them gradually. Drill a couple of holes (we typically use a 1/4" bit) and wait a few days to see where the humidity goes. If it barely drops, add a couple more, wait a few days and reassess.
One final note: when buying your first tank, get the largest tank you can afford and will fit in your home. Many people start off with a smaller tank and later have to upgrade when they acquire additional crabs. Another consideration is clutter, adding enrichment items like climbing logs, wheels, hides, etc can really clutter a tank and many people decide to upgrade the tank size so they can really deck it out. If you go big at first, you will save a lot of money and frustration in the end. When upgrading to a new tank, you may have to maintain two tanks for a while. Inevitably, you'll have at least one crab buried in the substrate when moving day comes.

substrate

This is one of the most critical components of the crabitat. The substrate will be utilized as a den for burrowing crabs and must be able to hold the shape of the tunneling and not expose them to hazardous materials.
It is recommended to only use a 5:1 play sand/Eco Earth mix. Play sand, the type used for children's sandboxes, can be purchased at Lowes, Home Depot, Ace Hardware, and most other home improvement stores. The sand comes washed and ready to use. Eco Earth is a brand name for coco fiber or coconut coir. It is shredded coconut husk and comes in either a bag of loose fill or in compressed bricks. If using the bricks, you must soak them using water treated with an aquarium water conditioner such as Seachem Prime. After soaking the bricks, they will have more than tripled in volume and needs to be spread out to dry. To speed the drying process, spread a thin layer in a roasting pan and bake for 30 minutes or so at 200 degrees. The Eco Earth does not have to be bone-dry but should not be very damp.
To measure the correct substrate ratio, use any size container, such a measuring cup or a bowl (we will call this a "scoop") and take 5 scoops of play sand and 1 scoop of Eco Earth. Repeat the 5 scoops and 1 scoop until you have mixed enough substrate to fill the tank to a depth of at least 6". If you have larger crabs, you need to have the substrate 3 times the height of your tallest crab. A jumbo crab may require 12" of substrate.
When mixing the substrate, it is easier to mix it in smaller batches in large tub or cement mixing tub. A 5 gallon bucket will work as well but can be more difficult to throughly mix. If you have to mix a lot of substrate, a powerful drill and paddle mixer can really speed it along and is much easier.
Your mixed substrate should be an even color, you should not be able to see layers of sand/Eco Earth. The moisture content of the substrate mix should be semi-moist and able to retain shape when the crabs tunnel. To test your mix, press your finger deep into the substrate, once you remove your finger the hole should remain intact. Do not get your substrate overly damp! This will lead to high humidity levels which pose some health risks to the crabs and will promote mold growth. There is also the potential for flooding but that's another topic all on its own.

HEating

Another one of the most critical components of the crabitat is the heat source. Crabs require a constant temperature between 75 and 82 degrees. This is achieved by using a UTH (under tank heater) also called a heat mat. These heaters are typically used for reptile enclosures and placed under the tank. We do NOT ever place them under the tank, only across the back glass, at or just above the level of the substrate. *The image above was taken during the substrate mixing process and is NOT a representation of where to place the heater! If you look closely at the image in the "POOLS" section you can see the bottom of the heat tape just above the substrate. That image shows the appropriate UTH/heat tape placement.
UTH come in many different sizes, DO NOT PAY ATTENTION TO THE TANK SIZE LISTED ON THE PRODUCT! To determine the size you need, measure the width of your tank and purchase a heater that will fit as wide as possible. Pre-made UTHs are typically sized for common aquarium sizes, you should be able to find something close to the width of your tank. Another option is heat tape, which is pictured above. Heat tape is cut to size and wired to a plug.
Attach your UTH with tape, either packing tape, duct tape, or the shiny metal tape used in HVAC applicatiions. Just a few pieces of tape on all sides will suffice.
You should purchase a thermostat or rheostat to control the amount of heat your UTH puts out. Thermostats adujst automatically based on their temperature probe readings. Rheostats are like a dimmer switch for your lights, you adjust them manually to maintain your temperature.
The crabitat pictured has a 12" heat tape that reaches almost the entire width of the tank. The room where the tank is kept had extreme temperature fluctuations over a 24 hour period. Initially, we tried using a rheostat but it was impossible to maintain a safe temperature. We had to purchase a thermostat (about $115) and set it to 76 degrees. The ambient room temperature rising during the day would cause the thermostat to shut off at 76 degress and the tank would heat up to 78 or 79 degrees, still within the safe range. This is a perfect example of why you should set up your tank and get everything "dialed in" and stable before adding your crabs.

monitoring heat and humidity

The crabitat should maintain temperatures between 75 and 82 degrees and humidity of 75%-85%.
To ensure that your tank's heat and humidity levels are within safe ranges you need to have accurate gauges. The cheap analog gauges sold at pet stores are not suitable, they're notoriously inaccurate.
Digital gauges are typically more accurate and come in a variety of styles. We prefer gauges that have a probe extending from the display. This allows your probe to be place where needed in the tank and keeps the display outside the tank and easily viewed.
We recommend having at least two gauges, one at either end of the tank. The probe should be suspended about 2"-3" above the substrate and not touching anything. Keep the probe roughly centered between the front of the tank and the UTH at the back, this will give you the most accurate reading.

Pools

Hermit crabs require both a freshwater and saltwater pool. The depth of the pools must allow your largest crab to fully submerge its shell. Food storage containers work great and the variety of available shapes and sizes make it easy to find just the right size and fit for your crabs and tank.
You must provide a way for the crabs to easily climb out of the pools. This can be achieved by many different methods such as making a ladder with various plastic materials or simply adding large shells or rocks in the pool. In the picture above, you'll notice the black mesh (Gutter Guard) attached at one end. We made holes in the plastic food storage tubs and used cable/zip ties (zip ties) to attach the plastic mesh.
When assembling your pools, we recommend doubling up the storage containers as shown above. This makes water changes easy and prevents the substrate from filling into the hole when the pool is removed and exposing crabs that may have burrowed under the pool. We added play sand to the bottom container to prevent the top container from nesting too snugly which would make its removal difficult and messy. Another tip: we wrote "SALT" and "FRESH" on two pieces of blue paper and laminated them. These laminated cards are set on top of the play sand, under the pool, this way we won't forget which pool is which. You can see a bit of blue peeking out beneath the crab.
One common bit of misinformation that, unfortunately, is still circulating is the recommendation of giving crabs a shallow dish of water with a sponge. It is mistakenly believed that crabs could drown in a pool and that they only require water for drinking. First, sponges should NEVER be used. They grow bacteria and mold, can accumulate filth in their crevices, and are just unneccesary. As long as you have an "exit ramp" there is very little to no concern for drowning. Crabs absolutely have to be able to enter the water to flush debris from their shell and re-fill it with water. Crabs require water in their shell to keep their body hydrated and their gills moist.
Many people use aquarium air bubblers in their pools. These are not necessary but do serve a purpose and are recommended. The air bubbles move the water which increases evaporation thus keeping up humidity. The movement does keep the water clear, reducing the accumulation of scum on the water's surface. One thing to be aware of and watch for is water splashing out of the pool and onto the substrate. Over time, this little bit of splashing water can cause flooding. To prevent this, use a bubbler rated for smaller aquariums or one with variable air flow. Another option for containing the water is a splash guard made from the lid of the food containers. Cut the food storage container's lid down to a size the enables the crabs to access enough of the pool while keeping the splashing water contained. Attach the splash guard lid to one end of the the storage container. Cut a hole in the splash guard lid to the diameter of the air tube, feed the tube through the lid and attach the air stone, now your air stone and tube will be secure!
When it comes to how often you need to change your pool water, the short answer is "it depends". You should monitor the water level, accumulated sediment, and scum on the surface. The frequency of water changes really depeneds on how many crabs you have, how messy they like to be, and the rate of evaporation. If you need to top off the water between complete changes, DO NOT ADD MORE SALTWATER TO YOUR SALTWATER POOL! When the water evaporates, the salt is left behind. You need to add fresh water to the pool to maintain the appropriate salinity.
It is important that you treat your water before giving it to your crabs. Use an aquarium water conditioner that removes heavy metals and chlorine. One of the best products is Seachem Prime. Follow the label instructions when adding it to your water. An alternative to treating your water is buying purified water but this is a much more costly alternative and not necessary. When mixing saltwater you must use salt made for saltwater aquariums. This can be confusing, there's products labeled "aquarium salt" that is used for freshwater fishtanks, this is NOT what you need. Do not use sea salt or other salt products found in the grocery store. We prefer to use Seachem Instant Ocean, it's an affordable, easy way to make the saltwater your crabs need. Before adding the Instant Ocean, be sure to treat the water with the water conditioner!

shells

Purple pinchers (Coenobita clypeatus) prefer turbo or turban shells with a round opening. Murex shells seem to be less popular but many crabs do choose to wear these. All of the shells we sell are hand selected and inspected for damage that would deem them unsuitable for hermit crab use. We use a digital caliper to accurately measure the opening so you know you are buying the size your crab needs.
As crabs grow (though molting) they will eventually need larger shells. They must be able to fully retract into the shell and block the opening with their large claw.
You need to provide at least 3-5 suitable shells per crab. Their lives depend on shells, they provide protection for their delicate bodies and prevent desiccation by retaining moisture. Failing to provide enough shells, or enough of the correct shells, can lead to fighting over shells and possible injuries or death.
You can keep the shells in a container (as shown above) that we refer to as a "shell shop" or scatter them throughout the tank. However, when left on the substrate, crabs are more likely to bury the shells.

enrichment

The crabitat needs to provide crabs places to hide, climb, exercise, and entertain themselves. This is where you really get to have fun and show some creativity.
Climbing structures such as jute rope ladders, tree branches, cholla wood, cocofiber mats, cork bark, and plastic mesh or vines should be added throughout the enclosure.
Exercise wheels/saucers for rodents are a favored item in the crabitat.
Leaf litter and real wood are both decorative and provide nutrition for your crabs.

food

Most foods in pet stores that are labeled for hermit crab use contain toxic chemicals and should be avoided. Feeding your hermit crab a varied diet is essential for their health. Below, you'll find a list of suitable foods from the required food groups.
Animal proteins: crab, chicken, beef, eggs, fish, insects, and shrimp. These can be served freeze dried or cooked. If cooked, do not add any seasonings! Alternate your protein sources, do not feed just one or two types of protein.
Fruits: apple, apricot, banana, blackberry, blueberry, cantaloupe, cherry, coconut, grape, kiwi, mango, orange, pear, plum, raspberry, and strawberry. These can be provided fresh or dried.
Vegetables: carrot, corn, beet, broccoli, spinach, sweet potato, squash, pepper, and mushroom.
Nuts: almond, brazil, cashew, hazelnut, peanut, pecan, pistachio, walnut, and nut butters.
Grains and seeds: chia, flax, quinoa, linseed, millet, oat, pumpkin, sunflower, teff, and wheat.
Supplements: algae powders, bonemeal, cayenne, crab shell, cuttlebone, egg shell, green sand, leaf litter, lobster shell, moss, oyster shells, paprika, spirulina, and worm castings.

creating the crabitat

Aquarium & Lid

substrate

HEating

monitoring heat and humidity

Pools

shells

enrichment

food