The best soil type for an African Mask plant (Alocasia or Colocasia) is a rich, well-draining soil that is high in organic matter. It should be kept consistently moist but not waterlogged. A mix of potting soil, peat moss, and perlite or vermiculite can be used to achieve this type of soil. Additionally, adding some fertilizer during the growing season can help keep the plant healthy and encourage growth.