I have used copper for over 30 years as a preventative in my QT, and have never had an outbreak of ich or velvet in my DTs. I always use a chelated form of copper (or cupramine) since the copper levels remain more stable that way. Be sure you have a copper test kit for the form of copper you will be using, and check levels frequently. My usual QT procedure is 3 weeks in copper, followed by 2 weeks of observation without copper in the water in the QT before putting the fish into a DT. I have to admit that I have tried hypo with no success. I think one of the problems with hypo is that it works well for ich, but not necessarily for other parasites, some of which may look like ich. OTOH, copper will eliminate all invertebrate parasites (and all other invertebrates in the tank, hence the advice not to use it in your DT).