I usually fix TMax films for 5-6 minutes. Kodak says 3-5, so I figure that or a tiny bit longer is fine. Always seems to work. Never have any kind of pink/purple/whatever cast on my negatives. After fixing I use the Ilford wash sequence of agitations and letting it sit 5 minutes after each water change. When I pour that water out, it's most definitely pink, even on the last water change, but the negatives always look fine.