Hi Mel,
I have just been through this hole rig ma roll, with the Vet here in Levin, I tell you what a long road to hoe, after about a month I finally got there
Picked up my Metro yesterday, proper Name for it is: Metronidazole 400mg Tablets is what you will be needing if it's for your Discus.
Dosage is: 1 x 400 mg Tablet per 40 Ltrs of Water.
Tablet must be crushed and dissolved in water before adding to your Tank, I was warned to wear gloves as this medication is Carcenogenic, and to dispose of the Treated Water with Care.
Prazi is Droncit, (NOT DRONTAL) you can get these at the Vets too, this is a Worming Treatment for Cats and Dogs, I had no trouble getting 10 of these tablets over the Counter
Good Luck