Hermit crabs are unique in that they have adapted to occupy empty shawls that they have scavenged to protect their soft abdomen. Hermit crabs will carry around this “borrowed” shell with them, produced by mollusk species, or risk being defenseless. The shell also helps hold and regulate moisture within the shell, which is important to ensure the proper functioning of their gills. If you have hermit crabs, having additional empty shells in your reef aquarium is essential for a peaceful tank environment. The addition of empty shells make great new homes for hermits as they grow bigger. 

Shell Changing

Hermit crabs may change their shells rather frequently, whilst others are more reluctant about changing shells. There seem to be some species differences, both in the frequency of shell changes and the shells preferred. Hermits may also prefer to change their shells before or after a molt, where they shed their hard exoskeleton to grow. 

Provide a Variety of Shells

As your hermit crabs grow, they begin to outgrow their shell. Eventually, the harmit must then search out a new shell as its home, to accommodate its larger size. Proving a variety of shells is also important so they change their shells as needed or desired. Hermits can be very picky about the shells they prefer, so it is necessary to prepare a good variety of shells for your hermit crabs. If you don’t have enough shells available, it can be stressful on crabs that want to change but can’t find a shell they want. The quality of the shell is important too, as shells that are cracked or have holes are not suitable, won’t hold moisture well, and crabs will not choose them. Additionally, if an empty shell is not available, your hermit crabs will not hesitate to become aggressive with other crabs and potentially fight to the death to obtain another crabs shell. By providing empty shells, you will reduce the likelihood of the hermit crabs competing for a home within your aquarium.

Choosing Shells for Your Hermit Crab

There is a huge range in the type, size and shape of shells available for aquarists to buy. We recommend a bit of trial and error to find the type of shell your hermit crabs prefer. The safest bet is to always provide lots of appropriately sized shells for each hermit.

  • Size: Have multiple shells with a similarly sized opening for each size of crab, as well as some that are slightly larger. Also, if you think that your crabs are in shells that might be a little large, give them some that are a little smaller. If you have a good range of sizes, the crab is likely to choose one that is the correct size (if the shell is too small, the crab will not be able to withdraw into the shell, and if it is too large, it will be difficult for the crab to hold onto and navigate around).
  • The Shape Of The Shell Opening (aperture): Provide shells with different shaped openings, at least before you know the tastes of your crabs. Openings vary in shape: round, oval, D-shaped, etc. When it comes to shells favored by hermit crabs, there tend to be distinct species preferences. 
  • Shell Type: It is nice to have some kind of variation in the shell type, but make sure you have some shells of the same or similar type as the type currently used by your crab.
  • Quality: Shells that are cracked or have holes are not suitable for regulating humidity inside the shell. To help keep the crabs’ gills moist, hermit crabs require intact shells that are able to retain a small amount of water.

You can often find painted shells in pet stores (some crabs are sold in painted shells, too). While these shells may look pretty, natural shells are a better option. The paint can flake off and create unpleasant fumes, as well as become toxic. Also, the paint might interfere with the shell’s natural ability to regulate the humidity inside the shell. 

Preparing the Shells

Before adding new shells to your aquarium, it is important to boil the shells for five minutes, drain them, and let them cool thoroughly. This will ensure they are sterilised, as often shells have been previously occupied. 

Should I Be Considering Adding Hermit Crabs To My Aquarium?

If you are battling to control your algae in your tank, or thinking about adding more interest and color to your set-up then hermit crabs might be the perfect solution! Hermit crabs have been crucial reef additions for many years as aquarists look for more time-efficient, economical, easy, and natural methods to keep up with tank maintenance. Hermit crabs are omnivorous scavengers, so will clean up any leftovers that have sunk to the bottom of your tank. Additionally, due to their small size, they can really get into all the small crevices within your rocks and corals, to thoroughly clean out any algae lurking to take over your tank. Their behavior is also fascinating to watch as they move their portable home around your tank. Our favorite reef-safe options include the Blue Leg Hermit Crab (Clibanarius tricolor), the Mexican Red Leg Hermit (Clibanarius sp.) and the Scarlett Leg Hermit Crab (Paguristes cadenati).

“I have ordered quite a few times and everything was always packaged great and arrived safe and fast. One of the best shops I’ve ever used.”

Robert C., Verified Buyer

We have several options to meet the needs of the size of your aquarium as well as the demand of your hermit crabs. You can opt for 10, 50 or 100 empty shell packs. If you’re unsure of how many would be suitable for your aquarium, feel free to Contact Us, we are always more than happy to help!