http://blog.bitfinex.com/announcements/bch-overview-information-bitfinex-users/
When will BCH deposits and withdrawals be available?
BCH deposits and withdrawals will not be enabled until we deem it is safe to do so. It is impossible to approximate the exact time, and it could potentially take 24 hours or longer. Do not send BCH deposits until we make BCH addresses available. This is very important. Furthermore, be sure to split your coins post-fork prior to sending us deposits.