Hi again I hope my first response to your question has helped with the use of ALA?
Oops I forgot to answer your issue on whether or not it is safe to eat fish due to Mercury contamination.
Okay I personaly don't eat fish, what I do is use fish oil supplements which are filtered to remove any heavy metals so they are mecury free which is good because you can get all of fish health benefits without the risk of contamination. The brand I recommend is Carlsons fish oil.
If you do insist on eating fish I would only use Sardines and Alaskan canned salmon as these have proven lowest in mercury.