Flaxseed oil or fish oil?

My daughter has c-ACC and i read on this site some where that either flaxseed oil or fish oil helped… and i was wanting to know which i should give my Daughter…thanks

We’ve been adding flax seed oil to our son’s food for years. We started to help him gain weight, and it did help! It also seemed to help with his constipation. It is a great plant source of omega 3’s 6’s and 9’s. We use Barlean’s brand.

I haven’t chosen a fish oil yet but I plan to. My concern is the potential for mercury. I believe there are a few brands that are third party verified to be mercury free but I need to find the information again.