Metro is actually very easy to overdose and I am actually surprised Seachem would recommend "a few weeks of metro". Their own metro product has specific directions to only dose three times maximum, I believe. Granted, this dosing schedule I do not agree with as it will not be effective and may create more issues when used improperly.
Its important to point out that metro functions as a gram positive antibiotic (as well as having very specific deworming capacities) and that misuse and/or abuse of antibiotics is flagrant issue within the aquatic (and medical) industry. Many common antibiotics and other meds are no longer effective due to the intentional (and unintentional) abuse that has resulted in resistant and stronger bugs. The use of any med needs to be given strong consideration to its necessity as well as the pros and cons of what is expected to be accomplished with its proper use.
All of this said, I do quarantine any new fish for four to six weeks minimum (up to three months) and every new fish is treated with a full course of praziquantel. Flukes in goldfish is an epidemic problem and I have yet to purchase a fish from ANY source (private or public) that did not scrape positive for flukes so I do not take chances with the healthy fish I already own.
