There are many fish oil products on the market. However we have found that many are poorly absorbed (i.e. patients get that awful "fishy reflux"), the concentration of the fish oil is very low and the fish are "farmed".
Farmed fish as a source of fish oil is an example of complete stupidity. Farmed fish become high in heavy metal contaminant - particularly lead and mercury.
Farmed fish are often fed GRAINS which completely changes the nature and quality of the fish oils they produce. Farmed fish omega 3 fatty acids will be significantly lowered. A fact that suppliers may neglect to tell you.
Further Reading:

This preparation is a rich source of the essential omega-3 fatty acids. UltraClean EPA/DHA Plus contains "ultra purified" EPA Concentrated Omega-3 triglycerides - fish oil that uses patented distillation and steam deodourising processes to ensure optimal quality, purity and low odour. It is enterically coated, meaning that it will pass through the stomach without breaking down prematurely and so be absorbed correctly within the small intestine. UltraClean EPA/DHA is flavoured with vanillin to minimise aftertaste.
Metagenics MetaPure EPA/DHAThis high strength, anti-inflammatory fish oil helps to maintain normal healthy triglyceride levels, cholesterol levels and cardiovascular health.
It improves mood and cognition in healthy people and temporarily relieves the pain and joint inflammation associated with arthritis. It is 20% stronger than Meta EPA/DHA and is currently one of the strongest fish oils on the market.
Nutrimedicine Omega 3 40:20
Omega 3 40:20 delivers highly concentrated, ultra purified EPA and DHA fish oils. Using the latest manufacturing technology, Omega 3 40:20 provides the highest concentration of EPA/DHA possible in one capsule.
Nordic Naturals ProEFA
An Omega-3, Omega-6 combination for prostaglandin series 1 & 3 production. ProEFA delivers EPA and DHA from fish oil and GLA from borage oil. Distilled for purity, ProEFA is an ideal supplement to ensure adequate intake of essential fatty acids from both fish and plant source.
Rosemary extract has been added for freshness, and natural lemon oil for palatability. Nordic Naturals are market leaders in purity, sustainability and freshness.
Nordic Naturals ProOmega Liquid
Nordic Naturals ProOmega Liquid contains 70% pure Omega-3, and is purified through molecular distillation to ensure the absence of impurities including PCBs and heavy metals. Taking a liquid fish oil increases absorption and enables you to get higher amounts of active ingredients per dose.
Nordic Naturals ProOmega Liquid offers a high concentration of both EPA and DHA, containing 875 mg of EPA, and 625 mg of DHA per serving. Nordic Naturals are market leaders in purity, sustainability and freshness. This really is a top-shelf fish oil.
Nordic Naturals ProOmega LiquidMetagenics MetaPure EPA/DHA - Highly Purified and Concentrated Marine LipidsOrthoplex DHA/EPABioceuticals DHA OmegaBioceuticals Ultra Clean EPA DHAMetagenics Ultra EPA Liquid - High Potency Ultra-Pure EPA LiquidMetagenics Meta EPA/DHA - High Potency Marine LipidsNordic Naturals ProEFABioceuticals OmegaSure Liquid Fish OilNordic Naturals ProDHA