Some rats are like that. They are nippers and they just play rough. I've had plenty like that. When my guys would start to play to rough, I would remove myself for the play area for about 10 minutes and then come back. I always offered treats when the play was good and soft. They are still sweet loving rats, just unique in their play behaviour.
My dude mochi has hormonal aggression.. He doesn't play nice with other rats so he has to be on his own, which he actually prefers anyway because he gets a lot of personal attention.... I had a question about when he gets hormonally aggressive... Obviously if I rile him up he will bite my hand or whatever skin is showing, And that hurts like an MFer.. I do what I can to avoid him getting to that point. I've learned his Triggers are paper rubbing together and a shkshskskkskhhshk noise, Along with His rump being rubbed (like being humped im guessing) and being tickled when hes on his back.
I recently put a small rat sized duck toy in his cage for him to take his aggression out on..... I was messing around with him today And doing all the things I shouldn't have, to get him riled up at the duck.. After a good minute of him being pissed off at the duck, He came to me for some pets... after some pets.. I put him back in his cage eoth a snack for a bit so he can calm down, and lower his heart rate. I am not about to cause my dude to have a heart attack lol... Was what I did detrimental to his health in the long run?... I don't want to keep doing something that will hurt him But it seemed like It helped him a bit to get some of that aggression out.
Please don't get all defensive and upset at me, I'm still fairly new to having rats.. He's technically in my second set of rats, and the first one thats agressive. I don't have the money to get him neutered, And I also do not trust the neutering process and anestesia on rats.. He's too good of a rat to lose too soon.