best kind fish oil?

I use Barleans. But I have used various brands over the years. I know that when I have gotten them at the drugstore or grocery store (cheaper kinds), they upset my stomach and make me burp and it is truly disgusting (sorry for the TMI). So even though it is hard on my bargain-hunter self, I stick to the pricier brands (get mine at the health food store) and have no problems at all. 

I have seen a naturopathic oncologist and he recommends the following brands for vitamins and supplements. Natural factors, carillons, ethical nutrients natures way and spectrum. He knows these are quality brands. Not to say the others are bad, he just doesn't know for sure.

I just read Dr Barry Sears' book The Omega Rx Zone.  Sears is the originator of the zone diet, and later he added fish oil to the mix.  He is adamant that fish oil supplements should be pharmaceutical grade.  I'm not so crazy about his diet recommendations, but I did feel convinced to give fish oil a try.  The bottle went really quick.  I'll be getting more.  I do feel like my brain fires on its cylinders a bit better with the fish oil.  ....I'm trying to get my brother to take it.  He's getting brain fog, arthritis and most recently elevated psa levels to the point of doctors wanting to to a biopsy.  According to Sears, fish oil will help all these complaints, as long as it's pharmaceutical grade taken in therapuetic doses.