When I used to run a quarantine (hospital) tank for new arrivals each one got 1 week of observation, 1 week of prazi, 3 weeks of cupramine (copper), another week of prazi, and then one more week of observation. Usually the copper started on day 2 of the first week of prazi and the second dose of prazi happened 2 days after I added carbon to remove the copper and first round of prazi.