Fish don’t make omega 3 oils, they ingest them from algae. So you can just cut out the middle fish and get them from algae yourself, in the form of algae oil supplements.
well the omega 3 to omega 6 ratio is the point of taking O6
How do you know how much O3 you need? So O6 is in plant-oils, how many O3 Capsules do you need to eat with your salad if you put olive Oil on it?
Fish and shellfish already have the perfect ratio, unless you cook them in plant oils.
I think the part about pollutant free shouldn't be overlooked. Some labels claim they have removed harmful things like mercury from their fishoil supplements. Eating fish and shellfish in large quantities eould certainly increase your exposure to that and other contaminants.
Smaller fish have negligible quantities of mercury and other pollutants, due to their short lifespan not allowing for bioaccumulation, as well as being much lower on the food chain. Herring, Anchovies, Smelt, Sardines, and even Mackerel or Trout, are all are excellent sources of EPA/DHA, and without any of the risks of larger fish.
Another option is krill oil, which contains large amounts of omega-3's and is low in mercury because krill (tiny shrimp-like creatures) are at the bottom of the food chain and eat only algae, unlike large fish which eat other fish and thereby concentrate mercury in their flesh.[1][2]
Incidentally, it's also possible to get DHA supplements sourced completely from algae.