While there has been a substantial amount of research on omega-3 supplements and their efficacy in preventing heart disease, recent analysis of the results of these studies did not find convincing evidence that omega-3s protect against heart disease.
If you still want to spend your money on them, I would also want to know what the source is. What kind of fish is it from? (Big fish accumulate more toxins than little fish with shorter life-spans) Was the fish wild or farmed? (Farmed is bad because of antibiotics in fish feed and contamination of wastes due to close proximity). Where did the fish live? (Atlantic is way more polluted than Pacific or Alaskan).
More to the point, supplements are just that. They are meant to SUPPLEMENT and not REPLACE a healthy diet. We should not be relying on a pill for health, be it for the heart or any other organ system. We should be eating healthy and avoiding junk. No amount of supplements will prevent disease if you eat a crappy diet and don't exercise and don't manage your stress.