For indoor tropical plants, you might also consider a mix of two parts coconut coir, one part pine bark, and one part perlite. This combination retains moisture well while ensuring good drainage and airflow, which is crucial for healthy root development. You can enrich it further with a slow-release fertilizer or compost to provide essential nutrients over time. Just be sure to check moisture levels regularly, as tropical plants can be sensitive to both overwatering and drying out.