I have no issue with anyone who wants to feed a variety of foods to their fish, just keep in mind that most high quality commercial pellets are made from a wide variety of raw ingredients.
Either way, no need to add "extra" fatty acids to fresh/frozen fish, nor to a high quality commercial feed. Vitamins is a different story.
If you really want to see to see some massive fish raised on a strict diet of pellets, visit a commercial sturgeon/caviar farm sometime. 8-10+ft fish, weighing from 100-200 pounds, all raised on a strict diet of commercial aquaculture feed since they were YOY. It's a multi-million dollar industry, with some of the primo caviar selling for as much as $5,000 a pound at a retail level. Also keep in mind that it can take over 10 yrs for a female to mature in captivity, so these commercial farms spare no costs in raising these fish to their maximum potential, and in optimum health.
If you are mostly feeding fresh/frozen, I would focus on supplementing vitamins, the fresh/frozen fish will supply all of the fatty acids required.
HTH