I have had bad results growing them in container.
Acai, seems to "sense" its in a container and will not grow well, they forever just stayed the same size.
All I can recommend is to plant the seeds directly into a big container from the start, I originally planted 100 seeds, almost all germinated, I put them in poly bags, and gave some away, I even sold some. those that were sold /given away, and planted in the ground were reported to doing well. those that remained potted, stayed the same size. I kept a few of the nicest ones, and I can say I have none now. they eventually died in my small containers. between 1-10 gallon. not sure why.