Hermit crabs need access to both fresh and saltwater at all times. They use these water sources to drink, bathe, and regulate their shell’s internal moisture.
Freshwater – Use dechlorinated tap or spring water.
Saltwater – Made using marine-grade aquarium salt (not table salt!).
Deep Enough to Submerge – Ensure they can fully soak but still climb out safely. Be creative use sewing mesh or anyway they can get out.
Hermit crabs breathe through modified gills, so dry air can suffocate them. The tank should stay at 70-80% humidity at all times.
Use a digital hygrometer to monitor humidity.
Keep the substrate moist but not soaking (like damp sand at the beach).
Add moss, water pools, or mist the tank if humidity drops.