Aquamat, how is your pleco doing.
If you use medications, you should use them for the whole duration of treatment. especially for bacterial infections.
Stuff from this point doesnt' relate to your pleco and your flukes - it is more like general advice for medicating.
if you are told you use tetracycline for example for 7 days.. and it goes away in 2, keep using it for 7 days.. this is so none of the bacteria that survive after the first 2 days become resistant to future doses of tetracycline...
sound a bit confusing but take the package instructions... over dosing moderately is good, under dosing is bad.
let's say you have a 10 gallon tank with rocks and gravel.. there is only really about 7 gallons of water in there, but go ahead and use 1 dose per 10 gallons... whatever the package says... I am not sure if this Rule of Thumb applies to salt water. apparently some species are really sensitive to copper.