I have to comment because I am literally sitting in a lecture at UC Davis about freshwater and marine parasitic disease, including ich. FWIW, one of the main take-aways I've learned in the past hour is the temperature-dependent life cycle speed of Crytpocaryon spp which is to blame in most of the ich cases we see. The temperature is important to consider when making your plan to teat for Ich. Treating Ich successfully in a 78 F tank can be done in 4 days, treatment beyond this is apparently not needed. Specific teatments we discussed was doing a quick look under the microscope to confirm cause, then choosing between copper or formalin treatment. Caution using anything with Malachite green because this is a considerable safety concern to humans (as is formalin).
Also the idea of leaving your DT fish-less for 72 days is at odds with what I just learned - the motile free-swimming parasite lasts only 48 hours without a fish host after which it dies, so 72 hours is likely over-kill and I'd be comfortable returning fish to the DT after treatment and resolution of signs. I have seen 6-8 weeks recommended in the past and I think it is generally accepted in the hobby but is possibly much longer than needed to clear the DT of parasites.
This is all new to me in the past hour and in previous years with Ich I was more aggressive with treatment so I don't want to advise against the advice above which is surely valuable since most of our success in treating disease in the aquarium hobby comes from our fellow hobbyists' anecdotal evidence and positive outcome experience.
My addition would be to consider my points and make sure stressor in the tank are at a minimum, ie good water quality, no wild fluctuations in parameters, no electrical shorting of equiptment etc.
Please let us know your treatment regimen and outcome - i hope it works out well!
