Preventatively treating fish - Question

[ReeseADHD]

Heyo, quick question about using the med trio to preventively treat fish.

I currently have platties and corydoras in qt with the med trio. In the Preventative Fish Treatment Section Cory says you're supposed to put in one dose of each med and let that sit for one week then I assume you're good? What's confusing me is that in the next section of the video he says if you're treating internal tape worms that you have to follow up 2-3 weeks later because the med can only kill adult worms and you need to treat them again once the eggs hatch. Should I assume my fish have tape worms; leaving them in qt and following up? 

[ange]

Assume that fish from any source come with infestations. They're difficult to control as a business due to the heavy cost. Usually when I quarantine new arrivals they're in a separate setup for at least a month before they meet their long-term tankmates. This allows time for 2 courses of dewormer and a monitoring period for other illnesses. This kind of schedule is required for most nematodes (camallanus and anchor worms), trematodes (flukes), cestodes (tapeworms), and protozoans (ich/velvet).