I've decided to drop putting fish oil on their raw food and instead give them one meal a week of sardines. They come as a complete nutritional package. Copied from the web:
Sardines the small, silver colored fish are also known as pilchards. You can enjoy them as a healthy snack or regular meal due to the various nutrients the fish contains. Pilchards are an oily fish, which are very rich in omega-3 fatty acids. They contain no carbohydrates, which helps to stabilize blood sugar levels. This fish is one of the rich sources of fish protein. It contains vitamins, A, B, C, D and E. Various minerals occur in the fish such as iron, calcium, selenium, magnesium, phosphorous and potassium. It is also one of the few foods that contain the antioxidant, Coenzyme Q10. Sardines have several health benefits.