Begonia roseopunctata, also known as the Polka Dot Begonia or Trout Begonia, can be an excellent choice for a terrarium due to its compact size and attractive foliage. Here are some considerations when growing Begonia roseopunctata in a terrarium:

1. Size: Begonia roseopunctata is a relatively compact Begonia species, making it suitable for smaller terrariums or as a part of a mixed plant arrangement in a larger terrarium.
2. Lighting: Begonia roseopunctata prefers bright, indirect light. In a terrarium setting, it is important to provide filtered or diffused light to prevent direct sunlight from reaching the plant, as it can scorch the leaves.
3. Humidity: Begonia roseopunctata appreciates high humidity. The enclosed environment of a terrarium can naturally provide the required humidity.
4. Soil and Watering: Use a well-draining soil mix specifically designed for terrarium plants. This will help prevent waterlogged conditions.
5. Temperature: Begonia roseopunctata thrives in temperatures between 18-24°C (65-75°F). Ensure that the terrarium is placed in a suitable temperature range and avoid exposing it to drastic temperature fluctuations or drafts.
6. Pruning and Maintenance: Regularly inspect the plant for any dead or yellowing leaves and remove them to maintain a tidy appearance.

By providing the right conditions of lighting, humidity, soil, and temperature, you can create a suitable environment for Begonia roseopunctata to thrive in a terrarium. Regular monitoring and adjustments based on the plant’s response will help ensure its health and beauty within the terrarium setting.