Terrible Advice Tuesdays (T.A.Tues.): A separate tank plumbed into your display tank works fine for a quarantine tank.
The rest of the story: Placing a fish in a separate tank, yet having that tank plumbed into your display tank such that the tanks share the same water is not true quarantine. The reason is that since the tanks share the same water source, any disease that could be on the fish in “quarantine” can pass into the display tank. Even if you use foam pads, filter socks or ultraviolet sterilization between the tanks, the disease can still cross contaminate the display tank.
To quarantine a fish properly, the quarantine tank and the fish have to be kept separate from the display tank. Any water, filters, nets, etc that come in contact with the quarantine tank cannot go back to the display tank otherwise cross-containation can occur. I’ll add that there is certainly no problem using display tank water to fill or to perform water changes on your quarantine tanks. Just make sure any equipment that touches the quarantine tank is kept separate from your display tank. If the equipment is going to come in contact with your display tank, it must be sterilized first!
Finally, keeping a fish in a separate tank that is plumbed into your display tank is a useful way to train a fish to eat certain foods. When the fish is in the separate tank, it won’t have to compete for food with the other fish in your display tank. The fish will still need to go through the full quarantine process before it gets placed in the tank though. Of course, while the fish is in quarantine, that’s a great time to train it to eat the food so why not double dip!Browse the Store! Questions?