They aren't. In order to overcome the omega-6 metabolic preference, you need to consume, at a minimum twice as much omega-3 oils as omega-6, but actually closer to 4x.
Twice as much omega-3 means eliminating olive oil, soy, most nuts, and many other foods. Or, alternatively, downing a pint or so of flax seed every day.
Everything you said is true except I can't see how fish helps in this case. You still need to eat a lot of fish (especially since most fish are very low fat, salmon is a good choice) and cut Omega 6 sources, if you want to make Omega 3:Omega 6 ratio 2:1.
Algae, and the fish that live on it, don't provide omega-3 oils. They provide the fully formed end products, DHA and EPA, so the metabolic bottleneck is avoided.
Twice as much omega-3 means eliminating olive oil, soy, most nuts, and many other foods. Or, alternatively, downing a pint or so of flax seed every day.