you will need to let your tank stay fishless for at least 6 to 8 weeks. You should set up a QT tank, and every fish you buy should be QT'd before going into your main tank.
14.SET UP A QUARANTINE TANK AND USE IT. Not using a quarantine tank is a sure way to introduce disease and parasites into your aquarium. You are either going to set up a quarantine tank when you begin your tank and prevent disease from entering, or you will set one up when you notice that you have a parasite in the tank. By quarantining all new introductions (fish, inverts, live rock), you will not have to worry about any kind of parasite in your display. A large tank is not necessary unless you plan on keeping very large fish. Usually, a 10 to 20 gallon tank will work just fine. Put a small hang-on power filter on the back, a little heater, and some fake decorations, and you have yourself a very simple, yet effective quarantine tank for $50-$70. That’s a small price to pay to greatly protect your animals and aquarium. And what’s better is this – you do not need to keep it running 24/7. Use it when you need it. Put a big block sponge in your sump or wet/dry to accumulate biological bacteria. Everytime you get a new animal for your tank, take the block sponge out of your tank and put it in your quarantine tank. This will move enough biological bacteria from your display to your quarantine in order to prevent disease. NOTE: Corals do not need to be quarantined UNLESS they are kept in tanks or a system that also has fish in it. If there is fish in the system, they too can carry a parasite with them.