Land hermit crabs need two separate pools — one freshwater and one marine saltwater — each deep enough to submerge the largest crab and each with a safe way out.
Do they need both fresh water and salt water?
Yes — two separate pools: one freshwater, one saltwater made with marine aquarium salt (such as Instant Ocean). Table salt and freshwater-aquarium salt are not substitutes. Condition your tap water according to the product’s own instructions — conditioning products differ, and a product that dechlorinates does not necessarily remove heavy metals, while others bind or detoxify specified contaminants. Treat for chlorine/chloramine as applicable and follow the label.
Mix marine salt per the product’s own package instructions. Instant Ocean’s own product page says to mix with ordinary dechlorinated tap or purified water — ½ cup per US gallon for small quantities — stir vigorously, aerate, then measure the specific gravity (recommended range 1.020–1.024 at 77 °F), adding salt or dechlorinated water to adjust. Instant Ocean’s own usage note: never mix salt in an aquarium containing animals — mix outside occupied pools, and only return animals after the salt is completely mixed, aerated, and adjusted. These figures are the product’s mixing recipe, not species-specific evidence of optimal salinity for Purple Pinchers.
Each pool should be deep enough for your largest crab to fully submerge, and every pool needs something the crabs can climb to get back out — a crab trapped underwater can drown.
Sources: HCA Basic Care Sheet (https://hermitcrabassociation.com/phpBB/viewtopic.php?f=51&t=92457); LHCOS Habitat Standards (https://lhcos.org/hermit-crab-care-education-standards/habitat-standards-for-ethical-hermit-crab-care/); CSJ new-owner checklist (https://crabstreetjournal.org/blog/the-newbies-guide-to-hermit-crabs/); Instant Ocean Sea Salt product page (https://www.instantocean.com/products/sea-salt-mixes/sea-salt) — read directly 2026-10-04
Editorial source review: October 4, 2026. This is an editorial draft of keeper guidance, not veterinary approval. Guidance generally focuses on Purple Pinchers (Coenobita clypeatus).
