Even if you're new to the world of hermit crabs, you surely know that the little crustaceans require a plentiful source of water to survive. They drink it, bathe in it and store it in their shells literally for dear life. Since hermit crabs are marine animals, saltwater is a staple for your crabby housemate. But if you don't happen to live near the ocean, you might be inclined to switch your crab over to freshwater.
They Can Tolerate It
Knowing whether your hermit crab can go in freshwater depends on what type he is. In general, hermit crabs need saltwater for mating and molting purposes; but some hermits come from areas near freshwater. These species, such as the Caribbean land hermit, naturally fare better than others when it comes to freshwater, using it to drink and for keeping their little gills hydrated when no saltwater is available. If your hermit is the type who relies on saltwater, providing brackish water -- water that isn't as salty as ocean water but is still saltier than fresh -- will at least provide some bit of salinity even if it isn't at the optimal gravity.
Both Is Best
Just because hermit crabs need saltwater, that doesn't mean they don't also need freshwater. You should give your happy hermit a supply of both, especially if you aren't sure what type of crab you have on your hands. You'll find he will take a dip in either and will drink from both types of waters. If you watch closely enough you'll see that your hermit crab will mix up his own special formula of shell water, using custom proportions of saltwater and freshwater.
Salting Up the Water Supply
You don't have to live on beachfront property to ensure your hermit crab has saltwater. You can make a supply of it using sea-salt products available at fish and aquarium supply stores. The packaging has easy-to-follow instructions to guide you through salting up freshwater to make it the right gravity. Using a gravity meter, also available at the aquarium supply shop, will ensure you get the salt-to-water ratio just right for your hermit. Noniodized table salt can suit; put 1 ounce of salt into 1 quart of water. Be sure to allow the salt to dissolve entirely and check the gravity with a meter before giving it to your crab.
Start With the Right Water
Your hermit crab might seem like a tough guy, but he really is pretty delicate. His system is so fragile in fact that, salted or unsalted, you can't give him just any type of water to bathe in or drink. Tap water contains all sorts of elements harmful to hermit crabs, including chlorine. Even well water and rainwater can contain toxins that will affect your little guy. You can get dechlorinating products at the aquarium supply store to will make your tap water safe for your hermit crab. Alternatively, using bottled spring water will save you the step of dechlorinating it before salting it.
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