Why do hermit crabs need both fresh and salt water?
All hermit crabs should have access to both fresh water and salt water at all times. New crabbers are often told by pet store workers and books that hermit crabs use fresh and salt water for drinking and bathing respectively. This is not exactly true, since hermit crabs will drink from either pond. They also store water inside their shells. Different species of hermit crabs mix their shell water by diluting different ratios of salt water to fresh water. The shell water keeps their abdomen and gills hydrated and functional. More terrestrial species such as C. brevimanus store more diluted shell water compared to less terrestrial species such as C. perlatus.
Why is tap water unsafe for my hermit crabs?
Never use untreated tap water for your hermit crabs' drinking water and food preparation. Chlorines (e.g. HOCl or NaOCl), chloramines, heavy metals and fluorines are harmful to hermit crabs. Fluorines are added to tap water in some states in the USA, but there are no products in the market that remove fluorines. If your tap water contains fluorines, you should use bottled spring water or distilled water. Tap water may be used for cleaning, as long as you rinse the surfaces one last time with dechlorinated water before wiping it dry. Use vinegar or lemon juice for stubborn dirt patches. Never use detergent or bleach.
May I use rain or well water?
Rain water may contain harmful substances that cannot be neutralised by a dechlorinator, so it may not be your safest option. Keep in mind that rain water collected in industrialised areas will be much more polluted than rain water collected from a rainforest far away from human populations. You may try using well water if it is relatively pure, but it is again a risky option, especially if it is prone to pollution.
How concentrated should the salt water pond be?
Instructions should be included with the packaging of each sea salt brand. Instant Ocean Sea Salt dissolves almost instantly, while other brands such as Red Sea Salt take longer to dissolve, but all are viable options. If you do not wish to follow the mixing instructions, use a hydrometer (not to be confused with a hygrometer) to measure the specific gravity of the salt mixture as more salt is added. The temperature of the water affects its specific gravity. You should aim for a specific gravity reading between 1.021 and 1.025 at room temperature. Make sure most of the sea salt has dissolved before taking readings. Remember to avoid 'hermit crab' salt products.
How often should I change the water?
Ideally, unfiltered water should be changed once a day, although some crabbers change it once every two days. For busy people who do not have time to change out the water frequently, consider setting up filters in the pond.
Should I put sea sponges in the water?
No. Harmful bacteria may accumulate in the sponges and they do not really help boost the humidity. If you have trouble keeping the humidity up, you should consider building a moss pit instead.
How do I set up filtered ponds?
You will need a twin outlet air pump, tubing and two small corner filters (one for each pond). The ponds need to be deep enough to submerge the filters. Attach tubing from the air pump outlets to the filters and then plug the air pump into the power point. You should change out the filter media such as the sponges and carbon once a month or every two months depending on how clean the water looks. Only replace half of the sponges so that you retain a small population of good bacteria in the water. Make sure that you build a secure escape route for your hermit crabs to climb out of the deep ponds; otherwise they will drown.
Do I need to bathe my hermit crabs?
You do not need to regularly bathe your hermit crabs, since they are capable of bathing themselves. However, you should give a warm salt water bath to hermit crabs that are newly adopted or were subject to a pest invasion. Follow the steps below to bathe your hermit crabs.
Thoroughly clean a container with dechlorinated, bottled or distilled water.
Dry the container by wiping all the sides with a tissue or towel.
Pour lukewarm salt water into the container. The water should feel neither hot or cold to touch with your wrist. The water should be deep enough to completely submerge your largest hermit crab. Make sure your hermit crabs cannot climb out of it.
Find another container and place a small, dry towel in it. It will be used for holding hermit crabs that have been bathed.
Rotate the hermit crab so that the mouth of its shell is facing you, then slowly place the hermit crab on the bottom of the bath tub, keeping them in that position.
Eventually, your hermit crab should come out of its shell to see what is going on. As it starts walking on the bottom of the bath tub, its shell water is flushed out. Take your hermit crab out of the bath and place them into the container with a towel to dry for a few minutes before returning them to your main tank.