Quote Originally Posted by Zyrendra View Post
they said the ones they sell weren't poisonous, although I don't know if what they say can be trusted.
They are poisonous. Your person from petsmart likely meant that they are not poisonous to humans. Not in the fatal sense of the word anyway. How poison they are to other amphibians and other animals varies most likely, but I've never seen it discussed with any details or examples.

As alane mentioned, their poison only causes a skin rash of varying severity in humans.

Care sheets that mention it do say not to mix species. If you do, it's your own experiment. I myself will not mix them with anything else that I want to keep. However, fish, shrimps and other things you may want to add to the water or land as feeders or cleaners are fine unless you develop attachments to them.