What size is the QT and what kind of filtration is set up? Depending on the size of the fish and tank, the more aggressive you need to be with water changes. To be honest, routine 50% water changes daily are recommended whether the params. are high or not. You can treat puffers quite readily with copper (Cupramine), but you just need to be more careful with dosages. Hyposalinity is the safest way, but also takes the longest which may or may not be in your favor. If you choose to use chemicals be sure that you adjust dosages according to water change %'s.