I've done the fish oil, and honestly never saw a difference. It was also recommended to me for depression and I never saw a difference there, either. However, now that ds is older and more controlled, I'm thinking of trying it again.
If you go that route, be careful of the source and quality. First of all, it has to be fresh. Secondly, know where it's from. Some of the ones on the market range from ineffective to dangerous. Some have high levels of mercury. Nordic Labs or Nordic Naturals is one very popular and highly rated brand. You can buy directly from them or from Kirkman Labs. You may also be able to find them locally by checking w/health food stores. They also have chewable ones!!! that don't leave a fishy taste, smell or fishy afterburp (yep, common problem). Those are the ones I've found to be the best. However, you also have to be careful to see exactly what your child needs. I found that not all of them have Omega 3 and 6. Nordic has low EPA, which my son supposedly needed. You also need to know the correct dosage for your child. Lower brands can upset the tummy.
Here's a site of reviews:
Reviews of Pharmaceutical Grade Fish Oil, Omegabrite, Sealogix, Nordic Naturals
I just found that site tonight, so haven't watched it over time. I was led to Nordic by DS' doctor.
My doctor and DS' doctor also liked Trader Joes' brand for effectiveness, and while it's cheaper, these gelcaps are horse-sized and have all the fishy burps and taste. To me it was worth it to get the better ones that he liked at Nordic-they are lemon flavored. The other thing suggested was cod liver oil. My son gags easily, and I wasn't really willing to subject both of us to the old spoonful thing.
Holistic supplements are great, but you have to know the dosage, the dangers and where you'll get purity. There are just too many variables (some contain this ingredient, some contain that....calcium is another one you have to be careful with). You truly have to work with your doctor and do your research. Kirkman Labs (where I get our supplements when I get them) will not give you advice, only product info. They won't try to sell you on anything, but will instead refer you to your doctor. That is smart. It's frustrating, because they simply wouldn't recommend anything to me, and I had a hard time at first with one doctor's instructions, but it's the safest, as these things can have the dangers and effectiveness of drugs.
HTH.