ACF will eat the Betta eventually before too long. ADF will probably need to be fed by hand because in a large tank the Betta will out compete it for food. With some careful attention and making sure the ADF is getting food it should work out. You just have to babysit the feedings, perhaps feed the Betta on one side of the tank then drop food for the ADF in front of him on the other side of the tank.