I had to gut my 125 a year ago because of ich.There are only 2 Proven ways to kill ich!Hypo and copper.I would advise against copper in your DT as well.You must remove all your fish,if this means taking evey piece of rock out ,do it,i did(yes,it sucks)Place fish in a hospital tank and start hypo.put all LR back in DT,and just leave your DT be for 6-8 weeks.Good luck,trust me its worth it to do this, it takes time and paitence,in a year from now you'll look back and say,i'm glad i did it.I know i do.