Hi Reba,
Fish oil capsules are safe as long as they have the words "molecularly distilled" on the label. That means they are not likely to have mercury contamination, which is associated with fatty fish.
I use the brand "Natrol" (purple bottle - get it at Walgreens), and keep them in the fridge for freshness and to avoid the fishy-burps. Yuck.
You're safer taking these capsules than eating tuna from a can I'm afraid... if you do eat Tuna, choose "chunk light" - Albacore (which is yummier) had a higher mercury content.
Joni