I had a BTA that I tried to feed after 2 days, it ate but regurgitated it shortly after. So, I tried 2 days later and it kept it down. All depends on the anemone I guess. I would say acclimate into tank = day 1, wait 3 days, next day attempt to feed. Basically 5 days total, like this:
Monday = acclimate
Tues - Thurs = wait
Friday = feed