I have 2 cats & live in a 600 foot square apartment. They are both fixed and are indoors only. They get along just fine when eating and sleeping on my bed with me. They even groom each other now and then. Miles is 18 pounds. He is big like a Maine Coon. He is 4 years old. Jasmine is 10 pounds and she is 2 years old. The problem is when Miles gets that amped up cat energy he chases after Jasmine and it's no longer fun for her. She hisses and tries to hide. I contacted the local humane society and the behaviorist said it sounds like play aggression. She recommended having play sessions with them which I've been doing with Da Bird feather wand. She also recommended using the Feliway multicat plug in which is a pheromone diffuser. I've used the Feliway original spray since the original plug in left my wall very oily when I used it many years ago with another cat. I've had Miles & Jasmine for 2 years. I'm afraid that Miles may injure Jasmine. He just went after her during our play session. Any suggestions would be appreciated!