If you aren't sick, do you take medications?
If fish aren't sick, why expose them to toxic chemicals for nothing?
Most fish medications are extremely toxic and the instructions are written so you only add enough to treat the disease. If you add a little bit too much, you kill the disease organism as well as the fish.
Quarantining fish is fine, but you should only add chemicals to their tank if they have an actual disease. Then add the correct chemical for that disease.
