Be really careful with water fasting. Even with juicing I ruined my metabolism. I've done several Water Fasts the longest being 7 days. When there is a lot of mercury toxicity you risk it being set free too quickly and it can become trapped in the thyroid and other organs and glands. Chelation along with lots of high fiber foods like organic veggies, colonics or enemas, etc will be helpful.
I'm not against fasting but really I do think that with the amount of toxins in the human body these days it's best to go slow. Eat raw food (well chewed or blended) for a few months first, then try juicing, then move into a water fast. I learned the hard way that jumping into a fast when you're toxic can be pretty detrimental. I don't think 20-30 years ago it would have been a problem. It's just the times we live in. Everything is polluted.
Cilantro isn't a chelator really. It will pull mercury into the blood but if the liver is toxic it may just recirculate it. Be VERY careful with tinctures and using large quantities if you have amalgams.