I have a beautiful green BTA that I have kept successfully for almost 2 years now, I have never once fed it other than what it grabs when I feed the tank, I have 4-65w PC's and it has only moved one time in the time I have had it, I have a pair of WS maroons that never leave it and spawn every other Sunday, I do a 10% water change every week and I run carbon in a canister which also gets changed every week.
My BTA has more than tripled in size since I got it and during the day when it stretches out and opens up all the way it is over 12" across, it has a full 1/3 of my 55g tank mostly to itself other than some polyps that have spread across the rock behind it over time but they don't seem to be bothered by it touching them.
I also did not attempt a BTA until my tank was at least 6 months old and then I lost 2 before aquiring this one, I think tank maturity, cleanliness and maintenance has more to do with success than anything.
My first BTA I fed regularly and it split and both died, my second one was too small for my huge maroon and she beat it up and it did not survive, this one was a good 6" across when I found it so it was able to take the beating from the female maroon. Good luck but take your time and be prepared to spend some time on tank maintenance!!!!