MC is right on the algae oil. It's a much better source than fish oil supplements. Virtually all, if not all fish oil is rancid or partially rancid. The "fish" smell means the oil is already going bad, so those fishy burps tell you that you're consuming a carcinogenic rancid oil. Check out the book "supplements exposed" by Dr. Brian Clement for more info on this.
Algae oil is much more stable. The DHA can be converted to EPA. Also you can take E3live which is a liquid form of klamath lake blue-green algae which happens to have both EPA and DHA which the other algae oils don't have. Soon there will be algae oil extracts on the market that have both EPA and DHA in them that will be a no-brainer for people to use over this horrible fish oil stuff being sold. Half of the fish ils out there are contaminated with mercury and again most are rancid, if not they go rancid in your body.
ALA has been shown to be converted easily to EPA and DHA in people who don't have excess omega 6's in their diets. The enzymes used to do this get used up by the omega 6's hence all the talk of people not having the ability to do this. Of course take a supplemental, plant based form of EPA and DHA to rest assured that you're getting these excellent nutrients.
Purslane is another land based plant that contains EPA and DHA. Not many like to talk about this one

It's a common garden weed in some areas! Look it up, research it and if you can get it, add it to yoru salads!