I found this post that helps. Hope the author doesn't mind me hijacking his post.
1. You may have trouble locating Levamisole, but Panacur (Fenbendazole) de-wormer is good as well and widely available (also used in Safeguard).
I would start ASAP, and repeat the treatment a few weeks after the first round is completed. Panacur comes in 1 gram packets, and 1/10 gram will treat their food plus a 20 gallon tank, so you'll have to divide the gram into equal amounts accordingly.
Before treating, do a partial water change, vacuum gravel, and remove any activated carbon from filter. It doesn't mix well with water, so grind the powder as fine as you can then shake in a container with a small amount of tank water. I use 1/8 cup in a baby food jar with a tight-fitting lid. Soak some food in the container for at least an hour with a pinch of garlic to make it more palatable and for its anti-parasitic properties. My fish spit out pellets and flakes, but ate bloodworms heartily, so I used them exclusively in further treatments.
When ready, pour entire contents into tank. Mix up little batches to medicate their food for the next three days, but don't add more medication to the water directly. After the three day treatment, do another partial water change and vacuum gravel. It's important to repeat this same treatment in about three weeks time for complete eradication. After both treatments, I fed frozen peas (shelled and thawed) to help them pass any dead worms, along with Jungle brand anti-bacterial pellets for a about a week, all soaked in garlic juice. The worms will perforate their intestines, and I did lose 2 Rams who were badly infested, but one who definitely had them hanging pulled through, much to my surprise. Also treated a BN pleco and ghost shrimp, who are still doing well. Good luck!
