Carlson's in my opinion is the best you can get from the health food store. Then you have Dr. Merola's fish oil which I believe is a step above Carlson's simply because he uses fish gelatin for the capsule as opposed to beef which is hard on the adrenals.
You also have fish oil from VitalChoice.com. All of these companies screen carefully ,from what i understand, for mercury and the other contaminants. I think Dr. Mercola and Vital Choice also have Astaxanthin, not 100 percent sure about Mercola, though.