how small is the toat? How many fish do you have to quarentine? Make sure they have ample room as you dont want to pollute your water too fast.
Lazy posted a good article on my post about ich. It talks about Myths of Ich and such. I would do as you have done so far, get them out, and get them treated. Once there is no sign of ich, i would keep them out for a week to see if they break out again. Feed them some food with garlic in it, it's been shown to "help".
In the article Lazy provided, it states that ich can last in your water without a host for around 6 weeks. So it might be wise to keep them out of the DT for that long if you dont want to treat the DT with Fishvet No-Ich which is reef/invert safe.