Giving my 14lb dog and 11lb cat fish oil, how much? Can you give to much?

I am wanting to give my cat fish oil, because she has flakey skin, and am not sure how much. I asked my vet and they had no idea. I also figured I could give it to the dog since he has itchy skin, but not sure how much. The cat Jamie is 2 1/2 shell be 3 in september, she a long hair maine coon mix who is 11lbs, I bathe her about every three months and use a gentle shampoo, because of her flakeyness. The dog Gizmo will be 2 in august, hes a smaller lhasa apso (he came from a puppy mill), hes 14lbs.