National Museums Liverpool Blog - Hermit crabs get a new home!

Bug House Demonstrator, Rebekah Beresford, is back again to tell us about her latest project in the Bug House at World Museum Liverpool. This time she has been giving the Hermit Crabs' vivarium a make-over! You can see the photos from each stage of the project on our Bug House Flickr set.

The Hermit Crab vivarium

After the success of the Indian Ground Beetles display earlier this year it was decided that some of our other vivariums could also do with a revamp! The Bug House hasn’t kept any mantids for over a year now and they’re incredibly popular with the visitors - so the next vivarium on the list was their display.

The new vivarium arrived from Exo Terra and was made by leading experts in the world of exotics. We got to work on siliconing in a glass partition, a third of the way along the tank to create a fresh water pool. Hermit crabs require fresh water so that they can mix it with salt water. The crabs then pull up into their shells their own preferred salinity reservoir from which they can breathe through. The fresh water pool in this vivarium will house a variety of aquatic invertebrates such as apple snails and gammarus (shrimp-like amphipods). The pool will also be useful for maintaining the humidity in the tank.

Coming from the Caribbean, these Hermit Crabs require humidity of around 70%. Hermit Crabs are avid climbers so it was important to factor this in to the design. A polystyrene wall made to look like rock work was ideal. It was easy to cut and wedged into place perfectly down one side of the vivarium. With some plants and bark attached the crabs would have plenty to climb and perch on.

Once the silicone had dried we tested it for leaks and luckily there weren't any! The pool was filled with gravel and the waterfall was set in place. The waterfall runs with a small pump set inside it. It’ll make the finished vivarium look quite impressive.

Hermit Crabs are renowned for being boisterous and particularly clumsy, so it was necessary to silicone some bark along the rim of the glass partition. This would prevent substrate from being kicked into the pool and also to allow leverage for the crabs to pull themselves out.

Whilst this was setting I had time to add the substrate to the land area. Hermit crabs dig themselves under ground for protection whilst moulting. Being invertebrates their skeleton is on the outside and moulting their skin to grow is a big deal. In the wild predatory birds could snatch them above ground level so they are forced under ground to do this. Even though hermit crabs are social creatures they are still opportunistic feeders. They would happily eat a moulting crab which would be soft and vulnerable and unable to protect itself, so it was important to factor in plenty of space to avoid this.

The next thing was to rehydrate the coco fibre to mix with the sand. Coco fibre comes from the husk of coconuts and is widely used in vivariums to provide sound air content and moisture in the substrate. The coco fibre was then added to the land area creating a gradient. This could then be mixed together lightly but the crabs would do a good enough job mixing it together themselves.

One of the last requirements for the vivarium was to add the climbing material. Drift wood is perfect for this because it’s so robust. I used smaller pieces along the climbing wall in steps for the hermits to climb over. Before it goes out on display I’ll add some bamboo and extra foliage.

Thanks to Phil from the aquarium, I was able to acquire a rainforest creeper called Devil’s Ivy. It’s commonly seen for sale in garden centres as house plants but its native to Asia. The plant was trained around the drift wood through to the fresh water pool. It’s a climbing plant and clings onto tree bark using its aerial roots. It’s also very hardy so will re-root itself quickly if the hermit crabs dig it up several times.

The Hermit Crab vivarium is now on display in the Bug House so come along and see them in their new home!