I would suggest you get him another gal friend or maybe even try just another different species playmate/cage-mate.
If ya didn't want any chance of breeding with same species, I would just keep in two different cages right next to each other so they can touch beaks but not mate. I haven't tried the latter myself to quiet screaming, maybe someone else here has. I would allow supervised interaction between the two Tiels though when you are around.
Then there is the option of rehoming him to someone who would put him in a large outdoor flight cage with a mate and allow him to live as natural and safe a life as possible = my #1 choice and I'm sure the bird's also if he could speak for himself.
