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Q&A with Keith, 8/21/09

  • Marine Depot
  • Aug 21, 2009


My question is about mysterious hermit crab deaths: I have been unable to keep red leg, blue leg or scarlet hermit crabs alive in my aquarium system. The first set of crabs I acquired lived for 3-4 weeks and all suddenly died within 2-3 days of each other. Most were dead inside their shells, although some crawled out and were a few inches away. What do you think the problem(s) might be?

There may be one or more reasons behind these mysterious deaths so we’ll cover all the potential causes.

The first thing you’ll want to consider is how you’re acclimating the crabs. They are sensitive to salinity changes so, in addition to acclimating for temperature (floating the bag 20-30 minutes), you should begin acclimating them to the salinity of your aquarium.

Personally, I use the drip method to acclimate my livestock. After floating new livestock in the tank, I carefully dump the bag into a bucket and use a drip line to carry saltwater from my tank into the bucket. Drip acclimators are inexpensive and acclimation tanks, like the AccliMate, are especially handy for the drip method of acclimation.

Test the water in 20-30 minutes and, if the salinity matches your tank water, go ahead and add your new critters to the aquarium. Don’t dump the bucket water into the tank. Instead, top of the tank with fresh saltwater.

The next thing to consider is water parameters. Is your nitrate level at zero? It should be. High nitrate levels can cause problems with invertebrates. Copper can also be deadly to invertebrates. I suggest using only RO or RO/DI water for top-offs and mixing saltwater.

Make sure your temperature is stable (small swings are OK, but large swings are a no-no), pH is stable (again, small swings are OK but best to keep it around 8.2 to 8.3) and salinity is stable.

And, while I don’t feel this is the culprit in your situation, it is worth mentioning to make sure there is nothing feeding or picking at your hermit crabs. If predation were your problem, you probably wouldn’t have found the carcasses of some of your crabs. However, if something were constantly picking at your crabs, it could cause them severe stress. Perhaps even to the point they would not be able to feed.

If you’ve addressed each of these issues and still feel there might be a problem, I encourage you to post the problem in our forum so the community can dig a little deeper into the underlying cause(s). You are also welcome to contact us directly for more personal one-on-one support.

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