found animal in tank

Question
QUESTION: we found a animal in our tank that has eight legs and pinchers.we got five crabs from med. to large in size. we have one female and four males.the animal is about 1/8 of an inch long. we didn't know if it was a baby(we heard it was rare to have babies) or some sort of mite or something that we should be alarmed about.

ANSWER: Dear Ron,
thank you for your question.
Baby crabs live as larvae (zoea) in the sea for a few weeks before coming to dry land. So you can rule out baby crab.
I suspect that you have a pseudoscorpion in your tank. They are called that because they look like scorpions without a tail, but they are not closely related. Pseudoscorpions form their own order of the arachnid family and feed on small insects, mites ect.
http://en.wikipedia.org/wiki/Pseudoscorpion
It it's really a pseudoscorpion, you can just leave it in the tank, it won't bother the crabs. If you want to move it, you can put it outside into leaf litter or another place where it can find shelter.
I hope I was of some help to you
Jennifer

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QUESTION: we live in ohio, usa. would it came in a shell from a crab we got a week ago? would it live outside in cold weather? thanks again, the kids will be learning about a new animal.

Answer
I don't think that the pseudoscorpion would hide in a crab's shell, but it's possible. Some species can live in the house, one species is actually called bookscorpion because they do live in and around books and feed on such prey as booklice. So it might have just wandered into the crab tank by accident.
As long as you find it a sheltered place like a woodpile, a pile of stones or a heap of fallen leaves, it will be able to survive. But you can also keep it in the house until it's warmer outside. You will need a glass or plastic container with a tight fitting lid, since pseudoscorpions can squeeze through tiny spaces, some moss, a leave to hide under and some sand. Pseudoscorpions can produce silk and some species build nests from silk, sand and whatever they find. You can feed it springtails, fruitflies (which can be ordered online or bought in pet shops, mostly for poison arrow frogs) or other insects/invertebrates that are smaller than itself. Offer a small moist piece of cotton for water.