I know some dechlor products react negatively with Purigen (those containing amines) to create toxic substances that can harm the inhabitants in a tank. I can definitely see not wanting to put water treated with one of these dechlorinators into a tank running Purigen, however, what if said product hasn't been used for a couple of weeks and then Purigen is added into the filter? Are those amines still active? Is it one of those issues where immediate contact would create a problem, but not in "aged" water? I just don't want to make anyone sick, but would really like to use Purigen to clear the tannins in my 80 gallon. The SeaChem Q&A page wasn't very helpful on that specific point.