Sources of omega-3 supplements

My experience with O-3 oils is that taste follows quality, which follows price.  Bad tasting oils are usually rancid (oxidized), which makes them not just useless, but actually damaging. (if you take capsules, it’s not a bad idea to occasionally bite one open to see if the oil tastes bad)

[[MORE]]Cod liver oil (CLO) is a good source of O-3.  Unfortunately, one complication is that fish tend to pick up a number of toxins, and those toxins tend to concentrate in their oil -- so the source of the fish used to make the oil is important.  I like Carlson's for that reason; they use fish from Norway and also test the oil they use for toxins, which is something I'm not confident that many other suppliers do.

Another issue is the high level of Vit A, which can apparently counteract some of the benefits of Vit D, according to some recent studies.

CLO also contains more than just O-3.  A somewhat better source is Krill Oil, although it's not cheap.  I've found Jarrow to be a good brand.  Both products are available from iherb.com.

Fresh fish oil should not taste bitter or fishy.  I'm convinced that a large number of the fish oil capsules contain rancid oil. I've also found that many people who think they don't like fish actually just don't like fish that isn't fresh. Even store-bought fish often tastes fishy, which is a clear sign that it's not fresh.

Another issue with rancid oil is that it can turn rancid well before it's possible to taste it.

If you take capsules, you might consider storing them in the refrigerator to help maintain freshness.  For bulk oil, adding some vitamin E to the bottle can help extend its shelf life.

Even if you don't use it on a regular basis, you might consider buying a bottle of Carlson's cod liver oil, just so you know what fresh, non-rancid oil tastes like. You might also try checking to see how your capsules change in taste over time: chew on a few when you first get them, and then repeat once a week or so. Any change is not good.

The issue with oil rancidity isn't unique to fish oil. I've noticed foods like bulk nuts sold at many grocery stores are also often rancid.  Once you identify the taste, you may be surprised at how prevalent it is.