Make sure you keep one per tank! I tried to put 2 in a 10 gallon with plenty of hiding spaces once. They attacked each other and both of them bit the other, and died in about 10 minutes.
I know! I have tons up here, and they freaking charge at you if they feel your presence. Most spiders I know just scurry away... not go into a suicidal one-sided battle head-on.