Crabitat: Substrate & Moss

This is where you discuss the conditions of your crabitat -- temperature, humidity, substrate, decorating, etc.
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Crabitat: Substrate & Moss

Post by HCADirectors » Wed Mar 13, 2013 2:06 pm

The products listed here are not all the crab safe products that exist!! These are just the most common ones, and the brands that are mentioned the most. There are many more products out there that are safe. If you have questions about something, ask in Crabitat Conditions before you use it.


Why is picking the right substrate important?

Substrate is extremely important for hermit crabs because of their need to be able to dig underground for months at a time to safely molt. Molting problems are the number one health issue that hermit crabs face, so offering a proper substrate can do a lot to keep them happy and healthy for a very long time. As with most hermit crab products, sand sold specifically for hermit crabs is not safe for them. Read on to find out why!

How much do I need?

At the very least, you need it to be twice as deep as your biggest crab stands tall. This will allow the hermit crabs to be able to get fully underground safely. However – more is better! When you have multiple crabs they will dig a lot, and they prefer to have a lot of substrate on top of them when they molt for safety. In order for the caves to not collapse, and for multiple hermits not to accidentally come across each other underground, three times or more is recommended. Some species, such as straws and Es, will be ecstatically happy with 10 or 12 inches of substrate, regardless of the crabs’ sizes.

We have a chart that recommends tank size and substrate depth. There is a full article called "Tank Size, Crab Size & How Many Can You Have?" located >here<.


Why does it need to be kept moist?

Substrate should always be kept moist enough for a hermit crab to be able to dig underground and form a cave. It needs to damp enough that it holds its shape when you squeeze, but not so wet that it drips or pools water. (We call that “sandcastle consistency”.) Too dry and it’s not diggable, too wet and you risk bacterial growth at the very bottom of the tank. Substrate should be mixed using salt water that is the same their drinking water in order to keep it fresh for a long time and cut down on the risk of mold growth. Substrate may also require maintenance such as spraying with fresh dechlorinated water on a regular basis in order to keep it moist enough since the moisture in it will evaporate over time. (Use freshwater to spray as salt does not evaporate, and spraying with saltwater constantly can lead to a harmful salt build-up!)

All water used in a tank needs to be dechlorinated, even when used for the substrate!!

What should you use?

Playsand and cocofiber are the two things that are regarded as completely hermit crab safe. They can be used by themselves, or mixed together for the best of both worlds. Many crabbers prefer a mixture of 5:1, which means that for every 5 equal parts sand, 1 equal part of cocofiber is used.

*New for 2015, Fluker's Farms has a pre-mixed hermit crab substrate that is made using playsand, cocofiber and sea salt. While more expensive than making the mix yourself, their pre-made mix is completely safe for hermit crabs and is the same recipe that most crabbers have been recommending for years. It is called Hermit Beach Sand Substrate for Hermit Crabs.

Playsand is cheap - less than $4 for 50 pounds, which will fill a 10 gallon - and very easy to find at any home improvement store. Because it has been cleaned and screened already, most owners will use it straight from the bag as-is with no extra washing or baking. Sand is sold in the same place as cement. It holds its shape very well when made sandcastle consistency, and generally stays moist for a long time. Pool Filter Sand is the same thing as Playsand, except it has been screened to a uniform size and should contain less dust. Playsand is made of ground silica.

Sakrete Playsand
Quiktrete Playsand
Pool Filter Sand

All purpose sand is another option. It has a bit more course grain size than playsand, and holds molting caves very well. It also tends to stay moist better than play sand. It has not been washed or screened, and it has a heavier clay content so any rinsing should be done outdoors. Many hermit crab owners use it straight from the bag, though.

Quickrete All Purpose Sand
Sakrete All Purpose Sand

Cocofiber is coconut husk that has been processed to be as fine as coffee grounds. It can be bought loose in a bag or compressed in a brick that you expand using water, and can be found at any pet store. The compressed bricks have an easier time if you use hot water, and you might want to use less than the directions state so that the cocofiber isn’t dripping wet once it’s ready. Cocofiber can be difficult to get to the right moisture level, and it should be kept on the dryer side rather than the wetter side so it doesn’t get funky over time. Cocofiber will boost the humidity level or solve most humidity problems you may have in your tank.

Make sure to buy the finer type of ground cocofiber as it is ideal for hermit crabs to dig in. The bark, fiber or chip kind are hermit crab safe and can be used to add some texture and variety to another substrate, but by themselves they are just too chunky to allow the crabs to form the caves needed for molting.

EcoEarth (compressed brick & loose) by ZooMed
Hermit Crab Soil (compressed) by ZooMed
Plantation Soil (compressed) from Exo Terra
Plantation Soil (loose) by Exo Terra
Forest Bed by T-Rex

Dry aragonite sand has been used successfully by some crabbers rather than using playsand. However, aragonite sand is calcium carbonate, which means it can possibly develop the same problems as calcium sand (see below) due to its porous nature and should be watched closely if used. It is larger grained than calcium sand and it will not clump or harden.

Kolorscape Playsand (Part aragonite, part silica)
Carib Sea Aragonite
Nature’s Ocean
Seachem Meridian

What substrates shouldn’t be used?

Hermit crab sands and reptile sands are actually a very fine calcium sand. While this may sound helpful, the sand used by itself is dangerous. This type of sand cannot be kept moist without a large risk of it developing bacterial growth, and as it starts to dry it can harden like a rock and trap or harm hermit crabs. Even when wet it clings to hermit crabs and causes them discomfort. Most of these sands have also been dyed, which can stain a hermit crab until the following molt. While this sand should never ever be used by itself, some crab keepers have reported success with using a bit mixed in with cocofiber or regular playsand.

Gravel of any size isn’t safe to use since hermit crabs can’t dig or make caves. It can be used as a decorative accent in the tank to keep messes down around water bowls, but it will eventually get mixed into the rest of the substrate. (This won’t hurt the hermit crabs, but you might lose the effect you were going for.) It should never be used as a primary substrate!

Coral or crushed shell is too rough and too sharp to be used on its own. A small amount can however be mixed into cocofiber or sand as an easy calcium snack for both hermit crabs above ground and those that are molting.

"Live Sand" sold for marine fish tanks is aragonite sand that contains bacteria and micro orgasms, and is sold wet. Aside from being drastically overpriced for use in a hermit crab tank, the organisms in the wet sand will start to rot if not used in a cycled fishtank (in water), and therefore this type of sand should be avoided.

While moss is a great thing to have in a hermit tank, it should not be used as a primary substrate as it does not offer any protection for them while molting.


Hermit crabs love moss! They enjoy hiding in it, and also snacking on it. Using moss can also help to boost the humidity levels of the tank if you are having problems. Most hermit crab keepers use something called a “moss pit” to add moss to their enclosure. A moss pit is a container of some sort (like a plastic tub or a shower caddy) that holds the moss off of the substrate, increasing the square footage of the tank and keeping the moss contained and clean for longer. It is usually deep enough for the crabs to completely hide in the moss if they wanted to.

What mosses shouldn’t I buy?

Never buy crafting moss or moss from the dollar store. Moss for decorative use has often been sprayed with chemicals and pesticides to keep it bug free and looking good, or it may have been dyed. Even if it says “terrarium” safe, it is probably not safe for hermit crabs.

What mosses are safe?

Mosses sold at the pet shop for reptiles are safe, although some have an animal safe dye that might come off over time. Organic mosses for Orchids that are sold at home and garden have also been used safely, and are often less expensive.

Moss that you collect yourself in areas that are free from pesticides and chemicals are also safe to use. However, there can be restrictions on the collection of moss due to overharvesting, so check the regulations in your area first.

What types of moss are there?

There are many different species of type of moss that are sold, and hermits enjoy them all! It all comes down to what you like to have in the tank, and different types can be mixed if you prefer.

Sphagnum moss grows in extremely wet area like peat bogs, and has a star-like shape to it.
Sphagnum Moss (compressed and loose) by ZooMed
Repta-Moss by Fluker’s
Sphagnum Moss by Mosser Lee

Frog and Terrarium Mosses are often sold in a sheet that still has earth attached to it. It is also known as “Hiawatha Moss”.
Frog Moss by ZooMed
Frog Moss (compressed) by R-zilla

Beaked Moss is another type of moss, and it’s generally looser and fluffier than the others.
Terrarium (Beaked) Moss by R-Zilla
Forest Moss by ExoTerra

Spanish Moss is not actually a moss – it’s really a bromeliad (in the tillandsia family) that grows in trees and is also known as “air plants”. Reptile Spanish moss is safe for use with hermit crabs, but it won’t behave the same as real mosses would.
Spanish Moss by Fluker’s
Last edited by wodesorel on Mon Aug 07, 2017 9:55 am, edited 1 time in total.
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