I use a few things to supplement, most of which have been discussed before.

Mostly I use Salmon oil each day, and Apple cider vinegar (the organic one with the mother in it, usually Bragg brand) a few times a week.

I also feed plain yogurt every day, a few spoonfulls as a treat. I have some powdered kelp and will give about a 1/2 teaspoon maybe once or twice a week.