A bird cage with dimensions of 43x61.5x125 cm is quite spacious and can accommodate medium-sized birds like cockatiels, conures, or even small parrots. Here are some suggestions for setting it up:

1. Vertical Space: Utilize the height by adding multiple perches at different levels. Birds love to climb!

2. Toys and Enrichment: Include a variety of toys, such as chew toys, foraging toys, and swings to keep them engaged.

3. Feeding: Use multiple food and water dishes placed at different heights to encourage movement.

4. Cleanability: Ensure the cage has removable trays for easy cleaning, and maintain a regular cleaning routine.

5. Safety: Make sure all materials in the cage are bird-safe and avoid any small parts that could be a choking hazard.

If you have any specific questions or need more tips, just let me know!