cat fight for "king of the domain"

I have seen ideas for aggressive cats and introducing new cats to a home, but I have an older cat who recently turned agressive to a younger cat who has been in the home for almost a year. I hope there are others who are willing to share ideas for my feline family. I have a 5 1/2 year old altered male who one day desided my 1 year old male needed to be killed. This is completly out of character for the 5 year old, so I took him to the vet to be sure he wasn't sick or hurting. He verified the 5 year old is physically fine. He felt the one year old male had matured, and getting him altered would restore peace in the home. The one year old has been "fixed" for over a week now and I have kept them seperated except for about an hour each day. I put each in their own carrier and let them be close enough to smell each other. The 5 year old still wants to attack the one year old. He will even hiss at the one year old from under the door when they are seperated. Is there a trick to getting them to accept each other? How long after a neuter before the testosterone level is sharply decreased? Will I ever have one happy family again????

It certainly takes more than a week for the testerone to leave the newly neutered male, so aggression will continue. You can use a comfort zone room diffuser from Farnum Pet in the meantime to help ease the situation, but it will be at least a few months more before the male simmers down. You can also use vanilla extract on both cats to help make both cats scent neutral. Put the extract under their chin, between their shoulders and on the base of their tail a couple of times a day for about a week.

When they do tangle, take a dark colored towel or blanket and toss it over them to disrupt them and keep you from getting scratched.