Hmmm, so your going to need about 8.5 400mg tablets for one treatment :roll:
Metro is ineffective after 8-12 hours so need to treat twice a day, with a near 80% water change in between each dose, need to complete 6 doses.
Was going to offer to send you some, but with the amount you are going to need, will be better for you to get them from the Vet.
Far easier to treat in a 40 Ltr tank, hence the 400mg per 40ltrs.