puppy dominance vs another puppy

Question
I have a 5 month old female min pin and just got another female ig that is 9 weeks. The min pin constantly jumps and bites on the ig. Now the ig is biting back. I cant tell if they are playing or if they are fighting. So far no blood. When should I stop them from this behavior and what can I do to deter it? When I walk them together, the min pin again tries to jump on the other one. I am referee all day. The min pin is trying to tell the ig that this is her place and she was here first. Just looking for some tips on how to resolve this. I am getting answers like them them at it to no dont let them bite each other. Awaiting any tips and ideas. Thanks.  

Answer
Many puppies love rough play.  Sometimes it is hard to tell.  Mostly I look for one trying to escape and not coming back for more. then it is time to separate them.   The key to most behavior problems is approaching things using the dog's natural instincts. Dogs see all the people and dogs in the household as a pack with each having their own rank in the pack and a top dog. Life is much easier if the 2 legged pack members outrank the 4 legged ones. You can learn to play the role of top dog by reading some books or going to a good obedience class. A good obedience class or book is about you being top dog, not about rewarding standard commands with a treat. Start at http://www.dogsbestfriend.com/ For more on being top dog, see http://www.dogbreedinfo.com./topdogrules.htm