Charles Harrison (owner of the referenced website) happens to hold a Ph.D.
I've purchased from Doc several times without complaint.
Flubendazole and Levaisole hcl are water column dosed.
+1. I used his recommended Levamisole water treatment of 23mg/L, repeat 3 weeks later. Though I did not order from him - given the number of tanks I had to treat and to have some left over for addition to QT protocol, it was cheaper to order "Vermisol", commonly sold for treatment of avians. Google turns up a number of sellers.
Flubendazole is supposed to work also, but will also kill snails.
NOTHING ELSE WORKS. I can't stress that enough.
Even Fenbendazole is iffy, in my opinion. The Angels Plus Fenbendazole flake was completely ineffective. Not all fish will eat enough, and even for those that did pig out, it was still insufficient to cure any fish in my case.
You can put more in food with dog dewormer, but still you may have fish that won't eat enough for an effective dose.
The Angels Plus Levamisole flake wasn't out yet when I had callamanus, so I haven't tried it. But since it's so water soluble that it has to be eaten within 10 seconds to deliver full potency, I expect it too will be hit and miss.