DHA Omega 3/6 ?

Not any of those products but seachem nourish I had good luck with. I felt my fish were healthier and more colorful

Waste of money if one is feeding a quality pellet food, but if only feeding fresh/frozen it's always a good idea to supplement with a liquid vitamin. (presoaking the food) When doing so I prefer Boyd Vitachem.
http://www.drsfostersmith.com/product/prod_display.cfm?pcatid=4998

I can't really add anything with regards to an improvement in color or overall health as I begin using it immediately on any species that can't be pellet trained, but the science certainly backs up the need for supplementation for piscivores kept in captivity and fed fresh/frozen as the main staple, especially vitamin C , E, and thiamin. (B1) A good read on that subject.

http://nagonline.net/wp-content/uploads/2014/01/NAG-FS005-97-Fish-JONI-FEB-24-2002-MODIFIED.pdf

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