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I'm thinking of getting a vampire crab or fiddler crab, some other semi aquatic creature for my 20 gallon long planted aquarium. I have a 24oz pickle jar that I plan on running through the dishwasher on hot (no detergent) a few times and sink it like the image below.

Example and source - Life Hacker enter image description here

My substrate is eco complete, so small gravel, see sample picture below (not my tank). enter image description here

My concern is whether my crab will be okay with the underwater habitat? (dry out okay, burrow)

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Unfortunately, as cool of an idea as this is, it won't work for vampire crabs.

I don't have experience with fiddler crabs, but according to the PawNation website, they could possibly work with this setup (along with some other species). Although I would still recommend researching any specific species that you're looking at getting, just to be sure.

The issue is that semi-aquatic doesn't just mean that the species can live in either the land or water, but that they need certain percentages of both environments to survive (For vampire crabs it's about 2/3 land to water). In fact, semi-aquatic is a good indicator that the animal is terrestrial, but likes water available to swim in occasionally.

This is the case with vampire crabs, the water in their terrarium is only used for drinking, molting, and breeding. Otherwise you will never see them in water (or at all really, they're incredibly skittish). The ideal vampire crab habitat is actually the same as a poison dart frog's, so you can follow a care sheet for them if needed.

Unfortunately vampire crabs are a pretty exotic species, where not much is known about their care. So when these crabs do make it into a pet store they are typically mislabeled, and placed in aquariums, where they will only survive for an extremely short period of time.

This is because the vampire crab's life-cycle starts out in the water, where they drop of their young. The young crabs will live in and around the water until they mature and their shells darken in color. Once vampire crabs are mature, they lose the ability to gather oxygen from water so easily, and while they still can for short periods of time (they still need to be able to in order to molt), the effort it takes for them to do so will kill them.


Here are some places to find more information about vampire crabs, unfortunately as I mentioned, they aren't documented very well, so information about them is scattered across forums.

http://www.arachnoboards.com/ab/showthread.php?227935-Vampire-Crabs

http://www.aquariumadvice.com/forums/f12/purple-vampire-crabs-148262.html

http://www.dendroboard.com/forum/lounge/71330-vampire-crabs-me-needz-more-info.html

http://www.panzerwelten.de/forum/showthread.php?tid=711

http://caresheet.net/animals/crustaceans/vampire-crab-geosesarma/

  • You don't explicitly say this, so I'm asking to make sure. What you're saying is that - even though there is a dry zone for the crabs with the bottle, it does not have certain necessary conditions for them to survive? Do you know of any specific reason why they need more dry land, or conversely, why they need to avoid too much water? – ton.yeung Mar 20 '15 at 1:06
  • @ton.yeung Sorry, I was writing it pretty quick. I've updated it with some more info. – Spidercat Mar 20 '15 at 13:41

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