Defender Bonus

Defender Bonus Icon
Defender Bonus is available to all trainers every 21 hours. When viewing the Shop, you will notice the Defender button (shown on right), which allows you to redeem bonus Stardust and Poké Coins for having Pokemon currently defending Gyms. You obtain 500 Stardust and 10 Poké Coins for each Pokémon at a Gym up for a max of 10.

This means you can get a maximum value of 5,000 Stardust and 100 Poké Coins for having 10 Pokémon at Gyms.