I'm sorry to hear about your troubles,but the cold hard fact about ich is ,it must be dealt with before you introduce fish to your DT.This is my stance on it....No miracle ich killer will work.... get your fish out...treat them, in a bucket if you have to,and do hypo....leave your DT fishless(inverts, corals can stay),and starve the ich to death...8 weeks minimum IMO...Its not easy,it takes constant monitoring, 2-3 times a day..but 4 months from now it will be a huge weight lifted of your shoulders..:Cheers:
Good luck...