1. Having a quarantine tank on hand is a very good practice to use if you frequently buy new fish. The quarantine tank will weed out any sick fish that could possible get into your aquarium and cause harm to the other inhabitants.
2. If you have a protein skimmer you should shut it off when you are adding medicine to your aquarium. The protein skimmer will remove any medicines added to the aquarium.
3. You need to have some healthy natural bacteria to process the wastes and chemicals in your aquarium. This will take around 4 weeks to grow naturally, but you can purchase products to speed up the process.