How to Make Salt Water for Hermit Crabs Under 20 Minutes

To make salt water for hermit crabs, mix about half a cup of marine-grade aquarium salt into 1 gallon of dechlorinated water, stir until dissolved, and let it sit for 10 minutes. That is all it takes. Hermit crabs need both salt water and fresh water in their tank at all times – salt water helps them breathe, stay hydrated, and molt, while fresh water prevents dehydration. The two should never be mixed in the same dish. Always follow the ratio on your salt package, since brands vary slightly. Here is the full step-by-step.

What You Need

• 1 gallon of tap water treated with a hermit crab or aquarium water conditioner
• About 1/2 cup of marine-grade aquarium salt (such as Instant Ocean)
• A clean mixing container or bucket
• A spoon or stick for stirring

Important: Never use table salt, sea salt, or seasoned salt. Only marine-grade aquarium salt is safe – regular salts contain iodine, anti-caking agents, and other chemicals that harm crabs. And always start with dechlorinated water, because the chlorine and metals in untreated tap water can hurt your crab even when the salt is correct.

Step-by-Step Instructions

Step 1: Pour 1 gallon of treated, dechlorinated water into your clean container.

Step 2: Add about 1/2 cup of marine-grade aquarium salt (check your package for the exact ratio).

Step 3: Stir well until all the salt fully dissolves. This takes about 1 to 2 minutes.

Step 4: Let the salt water sit for 10 minutes before adding it to the tank. This lets it settle into a safe, even mix. Now it is ready for drinking, bathing, and soaking.

Setting Up the Salt Water Pool

Use a shallow dish your crabs can easily climb in and out of. If the bowl is too deep or slippery, a crab could get stuck and drown, so add rough rocks, pebbles, or a ramp for grip. Place the salt water pool on one side of the tank and a fresh water pool on the other, so your crabs can move between them and pick what they need. Keep bath water shallow and around 75°F to 82°F. Both dishes should be deep enough for the biggest crab to submerge, always with an easy way out.

How to Keep the Water Clean

Hermit crabs drink, bathe, and sometimes poop in their water, so it gets dirty fast. Keep it safe with these habits:

• Always use treated water. Make every fresh batch with dechlorinated water – never plain tap water.
• Change it every 2 to 3 days. Do not wait until it looks dirty. Bacteria builds up before you can see it.
• Rinse bowls with hot water only. Never use soap or cleaners. Even a tiny soap residue can make your crab sick.
• Scoop out debris daily. Remove any food bits or waste from the water each day.

Why Both Salt Water and Fresh Water Matter

Each type of water does a different job. Saltwater supports breathing through the gills, helps with molting, and keeps the crab’s internal balance right. Fresh water prevents dehydration and supports everyday health. Hermit crabs store a custom mix of both inside their shell to keep their gills moist. Without either one available, a crab can get sick, fail to molt, or even die within days – which is why both bowls are non-negotiable.

Conclusion

Making salt water for hermit crabs takes just 5 minutes and two ingredients: marine-grade aquarium salt and dechlorinated water. Mix about 1/2 cup of salt per gallon, stir until dissolved, and let it sit 10 minutes. Change it every 2 to 3 days, keep both salt and fresh water bowls in the tank, and never use table salt or untreated tap water. That is all it takes to keep your crabs breathing, hydrated, and healthy.

Frequently Asked Questions