Treating Velvet?

[Aquattro]

It sounds like people dose the initial amount, then retreat without water changes, resulting, in my mind, a cumulative dosage much higher than suggested. I did read though, a couple of note on fish mortality blamed on too high of a dose. So, not sure. Bob Goemans in one article suggested 20mg/l, although most references say 10mg/l as a single treatment for 10 days.
I'll try your suggested method of a single dose, then a water change 5 days later with an adjusted dose.