Acropora SP is the most delicate of the corals we keep in captivity. You must have a stable system and optimum water parameters IE: Zero Am, No2 & No3, Alk 8-10 dKh, 400+/- Ca, pH 8.0-8.4 and temp between 77-83+/-. They need intense lighting, most need MH, but some can survive under PC or VHO. Water flow is extremely important, lots of gentle flow, but no direct blasts, pointing a powerhead directly at one is a sure way to damage or kill it.
Their skin is less than tissue paper thick, and it doesn't take much for them to stress out and either bleach (expel their zooxanthella) or to completely loose their tissue (dead)
Temperature acclimation is the most important. **Personally I float the bags just long enough to equalize the temp, then mount and place them in the tank without doing any water acclimation, my thinking is better water conditions are much more important than slow acclimation.
**This is my personal method, it works for me, but is generally not recommended!**
I picked up 4 frags from Dr Mac at the meeting, all of them are doing fine in my system, and I didn't get them home until around 10:00 that night.
A side note, the frags Dr Mac had at the meeting were the first he's grown out under 100% natural sunlight, and the coloration of them is so much better that anything I've gotten from him in the past (grown under 20K MH's)