He asked for the best, not the cheapest...
Personally, I don't have any goldfish at the moment, but have been keeping them on and off for about as long as I've had fish. IME, I've had great luck with the hikari line, saki hikari (purple) and hikari lionhead specifically. I found that my fish had great rate of growth with both foods, but they may not be the best choice for fish with floating issues. Mazuri also makes excellent gel food mixes that are known to be nutritionally complete, unlike any mixes one might whip up in their own kitchen. They would be vastly better choices for fish with any food related buoyancy issues, and are also exceptionally easy to medicate in the event that the need arises.