How to release Accessory Belt tension 2007 RS4

[joers4]

Newbie B7 RS4 owner here & I can't believe I can't figure it out but here I am! The sharp edge on the bottom of the tensioner looks like a pry point but no luck. How do I release the tension? Thanks for your help?

[delroyx]

I've been thinking about this belt recently. Does it & the tensioners have a service/replacement time or mileage interval?