Do Hermit Crabs Need Saltwater? Land Hermit Crab Water Setup Explained

Q: Why do land hermit crabs need saltwater if they live on land?

Despite being terrestrial, land hermit crabs retain gills rather than true lungs, and gills need moisture to function — which is part of why humidity is also a critical setup factor for these animals generally. Saltwater specifically is associated with molting (the process of shedding and regrowing the exoskeleton, also discussed for a marine species in our emerald crab molting guide) and, in the wild, with the larval stage of reproduction, which takes place in the ocean even though adult land hermit crabs live on land. A pet hermit crab isn't going to reproduce in a typical home terrarium, but the molting-related and general physiological uses of saltwater still apply to captive care.

By Hektor Jorgo Published January 6, 2026 Updated June 14, 2026 4 min read

A land hermit crab terrarium with separate dishes of fresh water and saltwater on a sand substrate

Quick Facts

Animal in Question: Land hermit crabs (genus Coenobita) — terrestrial pets kept in terrariums, distinct from marine reef hermit crabs
Short Answer: Yes — land hermit crabs need access to both a fresh water dish and a saltwater dish at all times
Why Saltwater Matters: Used for molting, gill moisture, and (in the wild) the larval stage of reproduction
Saltwater Source: Marine aquarium salt mix dissolved in dechlorinated water — not table salt
Setup Basics: Two separate, accessible dishes — one fresh, one salt — both large enough for the crab to fully submerge if it chooses
Not the Same as Marine Hermit Crabs: Reef tank hermit crabs (blue leg, scarlet reef) are fully aquatic marine animals — a completely different care category
Water Quality: Both dishes need regular cleaning/changing — stagnant water in a warm, humid terrarium fouls quickly
Common Mistake: Providing only fresh water, or using table salt instead of marine salt mix

If you've kept a land hermit crab as a pet — or you're thinking about getting one — "do they need saltwater?" is one of those questions where the answer is yes, but the reasoning behind it isn't always obvious from how these animals are typically sold and set up.

Short Answer

Yes — land hermit crabs (genus Coenobita) need access to both a fresh water dish and a saltwater dish, kept available at all times. The saltwater should be made with marine aquarium salt mix (not table salt) dissolved in dechlorinated water, and both dishes should be large enough for the crab to fully submerge if it wants to. This is a standard part of land hermit crab care, related to molting and gill function — not an optional extra for a particularly fussy individual. For context on how different this is from the hermit crabs kept in reef tanks, see our reef-safe hermit crab guide.

Two Water Dishes, Two Different Jobs

A proper land hermit crab setup includes two separate water sources:

Fresh water — for drinking and general hydration, the water source that's probably more intuitive for a terrestrial pet
Saltwater — made with marine aquarium salt mix, serving purposes that fresh water doesn't cover

Both dishes need to be accessible and appropriately sized — deep enough for a crab to climb in and fully submerge if it chooses, since submersion appears to be part of how hermit crabs use both water sources, not just sipping from the edge.

Why Saltwater Specifically Matters

Land hermit crabs are terrestrial, but they retain gills rather than developing true lungs — a detail that connects to why humidity is such a critical factor in land hermit crab terrariums generally. Saltwater is specifically associated with:

Molting — the process of shedding and regrowing the exoskeleton, a concern that comes up for crustaceans generally (see our emerald crab molting guide for a marine example of the same underlying process)
Gill moisture and general physiological function
In the wild, the larval stage of reproduction, which occurs in the ocean even though adult land hermit crabs live on land — not directly relevant to a home terrarium where breeding isn't realistically happening, but illustrative of how deeply tied to saltwater this species' biology remains despite its terrestrial adult lifestyle

Using the Right Kind of Salt

Marine aquarium salt mix — the same category of product used to make saltwater for marine aquariums — is the standard recommendation, dissolved in dechlorinated fresh water to the manufacturer's instructions. Table salt and most "sea salt" sold for cooking are not equivalent — marine salt mixes are formulated to replicate the broader mineral profile of ocean water, not just sodium chloride, and that broader profile is the relevant one for an animal whose physiology is built around it.

Don't Confuse This With Marine Reef Hermit Crabs

It's worth being clear that "land hermit crab" and "reef tank hermit crab" are different animals with very different care needs, even though both get called "hermit crabs." The species discussed in our reef-safe hermit crab guide — blue leg, scarlet/red reef hermit crabs, and similar — are fully aquatic marine animals, living submerged in a reef tank as cleanup crew. For those species, "needs saltwater" means "lives in saltwater, full stop." For land hermit crabs, saltwater is one of two water sources in an otherwise terrestrial, humid terrarium setup — a meaningfully different relationship with saltwater despite the shared name.

Maintaining Both Dishes

Both the fresh water and saltwater dishes need regular attention — a warm, humid terrarium is exactly the kind of environment where stagnant water fouls quickly, and dirty water in either dish isn't doing the crab any favors. Regular changes, along with keeping both dishes free of substrate and debris that can accumulate from a crab climbing in and out, are part of routine terrarium maintenance.

Quick Reference

Land hermit crabs (Coenobita species) need both fresh water AND saltwater dishes, always available
Saltwater should be made with marine aquarium salt mix, not table salt
Both dishes should be large enough for full submersion
Saltwater relates to molting, gill moisture, and (in the wild) larval reproduction
This is a different "saltwater" relationship than fully aquatic marine reef hermit crabs
Both dishes need regular cleaning — stagnant water fouls quickly in a humid terrarium
Providing only fresh water is a common setup gap in land hermit crab care

Frequently Asked Questions

Do pet hermit crabs really need saltwater, or is fresh water enough?

Land hermit crabs (genus Coenobita) — the terrestrial pets sold for terrariums — need access to both fresh water and saltwater, not just one or the other. This is one of the more commonly missed aspects of land hermit crab care, partly because they're terrestrial animals and it's intuitive to think of them as needing the same single water source a typical terrarium pet might. In practice, saltwater serves specific physiological purposes — related to molting and gill function — that fresh water alone doesn't cover. A setup with only a fresh water dish is missing something land hermit crabs are generally understood to need.

What kind of saltwater should I use for a hermit crab?

Marine aquarium salt mix dissolved in dechlorinated water — the same general type of salt mix used for marine aquariums — is the standard recommendation, not table salt or sea salt from a grocery store. Marine salt mixes are formulated to replicate ocean water's mineral composition, not just sodium chloride, which matters for an animal whose physiology evolved around that mineral profile. The saltwater dish should be large and deep enough for the crab to fully submerge if it chooses to, since submersion is part of how hermit crabs are believed to use the saltwater — for gill moisture and during the molting process.

Why do land hermit crabs need saltwater if they live on land?

Despite being terrestrial, land hermit crabs retain gills rather than true lungs, and gills need moisture to function — which is part of why humidity is also a critical setup factor for these animals generally. Saltwater specifically is associated with molting (the process of shedding and regrowing the exoskeleton, also discussed for a marine species in our emerald crab molting guide) and, in the wild, with the larval stage of reproduction, which takes place in the ocean even though adult land hermit crabs live on land. A pet hermit crab isn't going to reproduce in a typical home terrarium, but the molting-related and general physiological uses of saltwater still apply to captive care.

Is this the same as the hermit crabs discussed for reef tanks?

No — these are different animals with completely different care requirements. The hermit crabs covered in our reef-safe hermit crab guide — blue leg, scarlet/red reef, and similar species — are fully aquatic marine hermit crabs kept submerged in saltwater reef tanks as cleanup crew. Land hermit crabs are terrestrial pets kept in terrariums with sand/substrate, a humid environment, and — as covered here — access to both fresh and saltwater dishes rather than living fully submerged. The 'needs saltwater' question for each group means something quite different: for marine reef hermit crabs, saltwater is their entire environment; for land hermit crabs, it's one of two water sources in an otherwise terrestrial setup.

Sources & Further Reading

About the Author: Hektor Jorgo

Co-Founder & Marine Biologist

Hektor is a co-founder of Sea Life Planet and has kept reef and freshwater aquariums for over 15 years. He holds a background in marine biology and focuses on species care accuracy, water chemistry, and tank husbandry.