The White Spot Hermit Crab

Written by John Cunningham · Filed Under Invertebrates

November 27, 2008 · Print This Article

Crabs are not always welcome in the marine aquarium. Some of them could cause trouble, either blundering about and knocking things over, possibly interfering directly with corals or just growing too large.

There are some crabs however that often find favour with aquarists, and these are the hermits. They are quite comical as they wander about the aquarium, and at the same time are useful as scavengers. They can be colourful too, though this is usually the legs as this is the part that can be seen. The shell is not the crab’s own; it has been found empty or taken over from a snail for example. The crab keeps itself secure in its shell with a tenacious grip. If excessive force is used to remove the crab, then the grip will not be broken, but the crab’s body will break apart. The grip is so strong because remaining in the shell means survival, outside of it means death as the crab is highly vulnerable. The crab holds itself inside the shell with its rear pair of legs which slant forward to increase strength, and in addition the abdomen is shaped to fit the shell reasonably.

This is one danger from the hermit crabs, their need for a shell. I once had a large snail and a hermit crab in the same 4ft aquarium and for a while all went well. However, the hermit began following the snail about, trying to get at its flesh and generally upset it. Eventually it damaged the snail which died. The hermit crab was next seen in the snail’s shell. Though I couldn’t be sure, I wondered if I was at fault, perhaps the hermit had grown and needed a larger home. I would suggest that a small selection of suitable shells is left in the aquarium, so that hermit crabs can change home if they have a need.

There are several suitable hermit crabs for the aquarium, and provided there are no dangers present (such as for example puffer fish) a fish only system could be used, though there needs to be rocky structures present. The best habitat however is a reef system, where the crab can find security and its ‘cleaning’ activities are perhaps the most useful.

The hermit crab being focused on here is commonly called the white spot hermit crab, or the scarlet hermit crab, or the knobby hermit crab. There may be more common names demonstrating that for identification purposes the proper name is the best. In this case the proper name is Dardanus megistos.

http://decapoda.free.fr/illustration.php?n=5&sp=225

It is necessary with this crab for the reef to be securely built, though this generally applies to all hermits, particularly the larger ones. They are not particularly naturally destructive, but just clumsy. They could grow to around 4″ (circa 10cm) including and dependant on the shell they inhabit. Only one should really be kept or it is likely fights will occur. It is also necessary to exclude shrimps in general as the crab could eat them. The hermit crab should be seen during the ‘lights-on’ period but is also active at night. They are hardy in a good habitat.

Feeding is simple as the hermit crab appears forever hungry, constantly looking for food. They will take de-frozen lance fish, mussel flesh, crab meat, and almost anything else that is edible. Hence they are fairly good at cleaning up.

This particular hermit crab is not suitable for a small aquarium; one of around 4ft (circa 122cm) should be fine. Though the crab population should be restricted to one, an aquarium of this size affords space for other inhabitants to spread interest.

This is one species of hermit crab which is interesting and colourful. However, if the aquarist wishes to keep more than one, or keep one in a smaller aquarium, there are types that could be available. For example, there is the red reef hermit crab, proper name Paguristes cadenati. This could grow to around 1½” (circa 4cm). A trip to the local fish shop (LFS) is likely to turn up hermit crabs that are suitable for the aquarist’s particular system.

With proper attention to the habitat and some to other livestock, the hermit crabs are as said useful, interesting, amusing and hardy. Additionally they pose no problems with feeding. All they require is a new home occasionally.

Related Posts

Should You Keep A Fish Only Aquarium, Corals Only, Or A Mixed Reef? This decision is often taken in the planning stage, when considerations of equipment arise - what is needed? Some equipment is duplicated whatever the system...
What Is The Best Algae Eater? That is a difficult question, and one which I cannot directly answer because most algae eaters have a type they are most fond of and...
The Bubble Tip Anemone There are a few anemones that find favour with aquarists and this is one of them. As well as the name in the title they...
How To Change A Fish Only Aquarium Into A Reef Aquarium The aquarist running a fish only aquarium has gained a great deal of valuable knowledge about husbandry. He/she has also been able to keep fish...
Is Frozen Fish Food Beneficial To Fish Or Just Handy To Aquarists? Unless the aquarium is a reef with corals only, then there are going to be fish present. Whatever species these fish are there will not...

Related Websites

Big Male King Salmon [pic] The team fish is a King Salmon (aka Chinook) upper 30lb range was caught last summer with Captain Perry of Sea Turtle Fishing Charters. The big male...
45 Records Collectables -> Radio, Phonograph, TV, Phone -> Phonographs, Accessories Many of us remember, and many of us still own, 45 records. While all vinyl records...
Fishing Report: June 26, 2009 Lake fishing is about as good as it has been lately. Amador is offering good quality bass fishing with one to three pound fish in...
Microsoft to Refine Netbook Definition to Manufacturers.. And Charge More for Not Being Small Enough? Ugh. Microsoft is at it again. Reportedly, Microsoft is going to put some sharper restrictions around rules on what they define as a netbook and...