Hi everyone. This is my first post and I'm hoping someone will have some good advice for me. I have 2 dogs, they are sisters but from separate litters (same parents) they are a year apart. Loki is the oldest and she is 2 years old and Trinity is 1 year old. They are half Pit Bull half Tosa Ken Mastiff. They usually get along pretty good although the younger one, Trinity, tends to escalate very quickly when playing. They have had minor fights that always start from playing but no one has ever been hurt. I do not let them escalate or play in the house and although they are much much better it has taken pretty much my full attention to monitor them when I am home (when I'm not home there is never an issue with fighting). Anyway, the other day I took them both to visit my sister's dog (he is a lab cross) whom they know and play with on occasion. When I arrived at my sisters I make them sit before entering her home and once in make them sit at the bottom of the stairs till they calm down a bit. I released Loki (the older one) first as she is much calmer then Trinity. I kept Trinity on her leash and brought her upstairs she was really excited but the puppies were going outside to play so I let her off to join the other 2 dogs. With in about 2 min my dogs started playing very aggressively and it escalated to a very serious fight. They younger one, Trinity, would not stop attacking Loki and I had to get right in the fight to separate them. Loki has a couple pretty bad puncture wounds and trinity just a scrap. This scared the CRAP out of me! The dogs were fine being together after the fight and are still fine together but I'm scared that this could be the beginning of trend. I use pinch collars on both and even though they had the collars on at the time of the fight I could barely get them to react - especially Trinity. My plan is to keep Trinity on a leash with the pinch collar so that I can hopefully give a leash snap if she escalates. I know that I don't want to avoid these types of situations as she will never learn how to properly behave if I don't teach her. Both dogs go to doggy day care at least once a week and get walks 1-4 times per week on top of this. I am wondering if anyone has any other recommendations on how to prevent my dogs from escalating play time to a fight. Thanks!