Why Not Have A Hermit Crab?


The marine aquarium, be it fish only or reef, can be fascinating and beautiful. The reef aquarium is the one that attracts most aquarists and understandably so. Colourful corals sitting on rocks with various fish swimming about and maybe other lifeforms. Why not a hermit crab? They are different and interesting, sometimes amusing with their antics.

The aquarist needs to have some experience before considering a hermit crab. There’s a problem – how is ‘experience’ measured? Generally the aquarium must be fully matured not new and ready for stocking or not long after stocking, in other words reasonably ‘aged’, preferably six months at least. Seawater parameters, meaning temperature, pH, SG, ammonia and nitrite (the last two should never appear) need to be totally acceptable without high nitrates, the last indicates that overfeeding doesn’t take place. As an unscientific comment, the seawater needs to be very clean.

If the hermit crab develops a sickness it cannot be treated with copper. This is not a problem as they are already in a reef environment with no copper corals in the same way fish are.

Hermit crabs like a rocky environment with crevices and caves so the reef system is ideal. The fish that are in the system should be peaceful and small, not unusual for a reef system.

Though hermit crabs are not usually difficult to keep, they are a little delicate. This does not mean that they are fussy eaters or likely to be easily damaged, but they do suffer from a less than ideal environment. Therefore after being taken from the sea and transported they can often be below par and need a good environment and feeding to strengthen again.

When the crab is obtained from the store it should be transported home without delay. The bag should be hung in the aquarium to allow the temperature to equalise and a small amount of seawater discarded from the bag say every 10 minutes and replaced by aquarium seawater. Once this procedure has gone on for about an hour it should be safe to release the crab into the aquarium. Keep the bag and crab underwater and gently tip the crab out into a quiet corner as far as possible. Leave it alone and after a while the legs will appear and it will go off and probably hide though not all do, some start exploring immediately.

Feed the fish as usual and don’t worry if the crab doesn’t get any, wait for it to settle down, usually this doesn’t take long.

Hermit crabs get larger and need to adopt a bigger shell from time to time, so it’s necessary to ensure there are one or two sensibly larger shells lying about. The crab will inspect them and if interested change. The shells should be natural and not man-made ie plastic. From time to time the crab will get rid of its exoskeleton and this should be left in the aquarium as the crab could well eat it.

Feeding a hermit crab is not difficult as they aren’t fussy. Usually they’ll happily eat any algae available and also small algae pellets, just the one or maybe two. Fish food will also be consumed if any escapes the fish. To ensure they have enough, place some food – a bit of fish or shrimp – near them and see if it is eaten. It will soon be known how much the crab will eat in the same way as it is with fish.

So a hermit crab like other inhabitants of a reef system demands a quality environment. It also need some spare shells in case it needs to move to a new one because of growth. Also adequate feeding without overfeeding which again is the same as fish.

So next time there’s a visit to the fish store look for a hermit crab just for interest. If a purchase is considered find out the size it will eventually grow to. Also get a couple of shells for it to move into should it wish.

  1. Great write up on the hermit crab John! There are so many wonderful variety of crabs for us to explore in this hobby, and the hermit is one of my favorites. The best thing about hermit crabs of any variety? They don’t get picked apart by some of the more aggressive fish that would kill your typical green emerald or sally light foot. This allows hobbyists to keep them in fish only tanks and not just reefs! I love it.

    Great work John Keep it up

  2. Thanks. They’re great little characters aren’t they.

  3. It’s helpful to know the best way to take care of a hermit crab. I’ve recently started an aquarium of my own, so I decided that I might like to get a hermit crab to add to the mix. I thought that the information about the type of environment that hermit crabs usually like was very helpful. It’s good to know that they like rocky environments with crevices and caves. I’ll be sure to make my aquarium more rocky to help make the hermit crab I’m getting feel more at home.

  4. Glad the post was useful, also hope the new addition gives lots of interest and turns out to be the usual happy hermit.

  5. As a kid we would spend summers in Cape cod where there is an abundance of hermit crabs. I was obsessed with them! Now they creep me out a bit but if you can get past that, they’re very cool.

  6. Ha, they’re like little aliens. I just find them interesting and cute, sometimes funny.

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