Hermit Crab Shell Size Can Affect Growth

Hermit crab shell size is an integral part of their overall health and can affect growth! As well, the shape, aperature (opening), weight and even the color have affects on whether a hermit crab will choose a particular shell (it or not).

And when a hermit crab has no choice, and instead must live in a shell that doesn’t fit well, their health and development can be directly affected.

Hermit Crab Shell Growth Seashells 15 PCS (7...

Shell size

Hermit crabs rely on shells to protect their soft, moist bodies. The shells they choose need to be a good fit in order to allow for good growth, development, movement, water retention and even for reproduction (when in the wild).

Provide multiple extra shells for each hermit crab in your habitat.

Multiple shells allows for hermit crabs to do what they love… try on shells! In the wild, hermit crabs are known to try on many different shells until they find one particular one they like. And most often, once a hermit crab finds a shell they like, they’ll stay in it until their next molt.

Sometimes hermit crabs will choose a shell that looks like it doesn’t fit. Other crabs will try on shells much more frequently than others. Because this behavior isn’t predictable and each hermit crab seems to have different behaviors and shell preferences, it’s very important to provide enough extra shells.

Hermit crab growth can be stunted by a shell that's too small

When a shell is too small, it can limit the growth and development of it’s moist body parts being protected inside the shell. A shell that’s too small can also affect the mobility of the hermit crab which can be detrimental to it’s ability to protect itself, to climb and maneuver, forage for food, and soak and retain enough water inside the shell.

In the wild, a shell that’s too small can also affect the amount of eggs a female hermit crab can carry. This egg “clutch” becomes compromised. A healthy female hermit crab can carry around 50,000 eggs, the vast majority of which won’t survive.

Shell size matters

Shells that are too large can also pose a problem for the hermit crab inside. However, shells that are too large are a much better choice than shells that are too small.

When too large, hermit crabs will struggle mostly with mobility. And if the shell is a medium to heavy type of shell, their ability to climb and maneuver could be limited.

Larger Purple Pincher hermit crabs tend to prefer Turbo Shells

Shell opening (aperture) size also matters

A too-small shell means the hermit crab will protrude too far out from the shell opening (aperture) and be more vulnerable to injury, predators.

Hermit crabs should be able to retract fully into their shells. Once inside their shell, their claws fold together to form armor protecting the opening of their shell. If the shell is too small, that natural protection is compromised.

Different types of hermit crabs have different preferences for shell sizing and shapes. Purple Pinchers (like the one pictured above) tend to prefer the round opening, medium-weight and compact spiral of turbo shells, as they grow larger.

It’s always important to know what type of hermit crabs you have, and what their shell preferences are in the wild. For more information on types of hermit crabs, with photos, see my blog post here.

Hermit crabs need to choose from multiple shells to find the best one

Provide plenty of extra shells. They don’t all have to be inside the habitat at the same time. But there should always be 2-3 extra shells for each size hermit crab available to them. Then, for extra stimulation and happiness, rotate the extra shells periodically.

Hermit crabs are HAPPY when they get new shells to try on! Consider keeping lots of shell types and sizes, and rotating them every few weeks.

See my blog post on Hermit Crab Shells here, which includes lots of types of shells plus ideas on creative ways of storing your collection of extra hermit crab shells!