Wellness always has $5 off any size bag coupons on their website. Just do the “check your bag” select some random stuff, and then at the end you can print your coupon. You can only hit print ONCE a month (maybe twice, just depends on when they reset it), but a window will come up and ask you how many you want to print. I usually tell it 10. In addition to those coupons, Petco puts out $3-5 off Wellness coupons as well, and most PetSmarts will take a store/competitor and a manufacturer coupon on each item, so you can potentially get $10 off a small bag of Wellness, provided you have both Petsmart and PetCo in your area.
With out coupons, Racheal Ray Zero grain is also good. They also put out $3-5 off any size bag coupons, as well. I usually just google “Racheal Ray dog food coupon” as I can never navigate through the website.
