A great way to increase your tank’s humidity naturally is to add natural moss to your tank.
[3] X Research source It increases the humidity, and hermit crabs eat it.
Look for moss like Fluker’s Reptile Moss at your local pet store.
Sponges also work well, and can also be found at a pet store.
But sponges get dirty easily and need to be changed out every two to three weeks.

Many crabs also like to bury and even molt in damp moss such as Fluker’s Reptile Moss (not decorative or Spanish moss!)

If you want to go the extra mile, you can sterilize your sand substrate. [6] X Research source Sand can be sterilized in the oven. Put the sand in a large roasting pan (one used only for this purpose!) and place it in the oven. Set the temperature to 250 degrees (F), (120 degrees Celsius) and let it be for about 2 hours. Once every two to three weeks, boil all the shells and dishes in your tank in a pan of dechlorinated salt water. Doing this will insure that that mold and bacteria will not grow and harm your crab. Allow the bowls and shells to cool before placing them back in the “crabitat”.

Natural toys: Natural rocks and seashells that you pick up at the beach are great things to scatter around the “crabitat. " Clam shells even make great food dishes. Just make sure to boil them in boiling water so that they become sterilized before you place them in the tank. Plastic toys: Plastic plants made for reptiles are great for crabs to climb and hide in, just remember to use the lid of your tank so the crabs can’t climb out. Make sure they aren’t eating the plastic, and remove it right away if they are! Never use reptile “half pine logs”, as pine is an irritant to the crabs and can be toxic. [7] X Research source

If you have large and small crabs together, you can put small rocks or a small natural sponge in the water dishes so that it is deep enough so large crabs can let water in its shell, but small crabs will not become trapped in the water dish and drown. You can buy aquarium salt for marine fish (not freshwater fish) from most pet stores and a little goes a long way. Never use salt intended for human consumption because the anti-caking agents can be harmful. Most hermit crab brand salts are also table salts. Pre-mixed “hermit crab water” does not have the correct salinity. Use a brand like Instant Ocean, Oceanic, etc.

If you don’t want to dechlorinate tap water, you can use spring water instead. However, make sure nothing has been added to the water. For example, Dasani water contains magnesium sulfate “for taste”, and that is bad for the crabs.

The most common type out there is the Caribbean (Coenobita clypeatus,) which is also called “PP” for purple pincher due to, you guessed it, its large purple pincher. Wild Purple Pinchers are found in the Caribbean Islands. [12] X Research source Most likely, when you see a hermit crab in a store, you will be seeing one of these guys. The Purple Pincher is the best one to start with because the others are more delicate and require much more detailed and intense care. The other types are Rugosus “Rug” or “Ruggy” (rugosus), Strawberry (perlatus), Ecuadorian or “E” (compressus), Cavipe or “Cav” (cavipes), Komurasaki “Viola” (violascens), Indonesian or “Indo” (brevimanus).

Once you get them home, they go through a “De-stressing” period that can take as little as a few days and as long as two months. During this time, change out their food and water regularly and do not disturb them. Sometimes, even with the best efforts of even the most experienced crabber, hermit crabs can succumb to Post Purchase Stress (P. P. S. ), and die. [13] X Research source

If you have a sick crab, don’t panic. Keep an isolation tank in a closet with enough substrate to dig under completely and ample food and water. If a crab is acting sick, he may be about to molt. This tank should also be kept with proper humidity and temperature as was mentioned previously.

Purple Pincher Hermit Crabs prefer the shells with round, circular openings. They will choose circular openings over the oval openings. Ecuadorian Hermit Crabs will prefer an oval opening, because they have flatter abdomens. Never buy painted shells! Although companies may claim the paint is safe, the paint can chip off, and if the crabs eat it, it can be toxic. [15] X Research source Most hermit crabs, when presented with a choice, will pick a “natural” shell over a painted one, even if it’s not the right size. See the Warnings for information on what kinds of shells to avoid.

Hermit crabs love silver sides and shrimp that are fresh, freeze-dried krill, blood worms, etc. , and other seafood. You can normally buy these fishy foods at your local grocery store. If you cook, set aside a piece of steak or chicken, non-marinated to grill lightly for the crabs. They also eat raw meat. If you have more than twenty crabs or so, try getting a fish head from a local fish market. They are usually happy to give them away. You can put all of your crabs in a large tank or a large clean Rubbermaid storage container, (clear, no lid, or lid with VERY large holes cut in it) drop in the fish head, and a water-bowl, and leave them in there to eat for a few hours. You will mostly likely not want to do this very often, since the stench is pretty bad, but your crabs will love you for it!

Hermit crabs love fresh fruit like pineapple, apple, pears, grapes, cantaloupe, watermelon, mango, papaya, strawberries, bananas, etc. Wash your fruit thoroughly before you cut it, to avoid pesticides. Crabs will go crazy for coconut shavings. Hermit crabs will also eat natural peanut butter on whole wheat toast, hard boiled eggs, egg shells (boiled), popcorn (plain, unsalted and unbuttered). Avoid anything from the Allium species of plants (onion, garlic, etc. ).

Remember that they need humidity. Typical house humidity is only 40% and even less with AC and heat. When a crab’s gills are exposed to low humidity it feels similar to how we feel when we hold our breath for too long.