If you are in the states, there are some excellent meds available. These are either for specific types of internal parasites and/or worms. Some may be dual meds that treat internal problems including infections. I keep a number of the below in my fish med box (marked with an *). The things below are also found in commercial medications in the ingredient list,
- Praziquantel* commercially available- Treats flukes, tapeworms, flatworms, and turbellarians. I use PraziPro by Hikari. There are other good choices.
- Metrodinazole* commercially available- also an anti-biotic- best if eaten but can be added to the water and will not be as effective. I use SeaChem's product.
- Levamisole HCL* serious treatment for Camallanus- a broad spectrum anthelmintic effective against nematodes.
- Flubendazole* Read
Flub.Info also treats tapeworm, velvet and Ich. Active through adsorption into the fish’s skin and gills doesn't have to be eaten to be effective.
- Fenbendazole
it is not absorbed through their skin or gills, so it must be eaten to be effective.
(The last 3 medications are all available here which is where I get mine:
http://www.inkmkr.com/Fish/ItemsForSale.html )
As with any fish med. you should do more research on any of the above before buying and using it. Also, these medications should not be mixed- use only one at a time.
Also- for the meds that should be fed, I would make my own medicated food. Whatever food(s) the fish normally eats work best. However, if a fish is not eating they don't help. If the fish is eating i would pick it's faborite food that it will eat almost as soon as it hits the bottom. Once in water medicatrf food can let out the med into the water in fairly short order. If you are feeding medicated food, no other foods should be offered and you may need to mask the taste of the med.