We already know that we are supposed to be eating fish twice a week. Fish are a truly healthy source of protein and the oily kinds of fish such as salmon, tuna, sardines etc deliver heart and brain healthy omega 3 fats which you have probably also heard you should be getting in your diet.Now the question is which are the healthy fish and which are not because all fish are not healthy and the source from where they have been caught also is factor.Many tuna fish are high in mercury but Albacore tuna fish has much lower mercury rate and contaminant ratings and those fish which are caught in colder northern waters have higher omega 3 counts.