How to know when it is enough?

[Turin Turambar]

My Harlequin Rasbora got sick 2 weeks ago, had some kind of spots/ulcers and I treated her with anti-bacterial medicine in the Q tank. Fortunately, she is recovering and she started eating few days ago.
Now - how should I know when she's totally ok and ready to return to the community tank?
Maybe the bacteria is still presented in the Q tank but she is rising the immunity to that now?

Thanks.

[OrionGirl]

I always think that longer is better. I'd wait until the fish is completely healed and has been eating normally for a week before re-introducing the fish to the main tank. The fish should no longer be a vector for transmission if it no longer has the open sores. It's unlikely that the bacteria caused the problem--it most likely infected the fish following stress or injury related damage to the slime coat. This means the bacteria was already present in the main tank, so this fish won't introduce it. My reasoning for the longer quarantine is that this allows the fish to return to full strength. It's likely going to be bullied on return, and being at full health will reduce the odds of it being injured again.

[wetmanNY]

There's the permanent possibility that a fish cured of visible symptoms of bacterial infection is still a sub-clinical carrier that can spread infection. The common kinds of bacteria that cause disease in individuals with weakened immune systems are Aeromonads and Mycobacteria. They are everywhere in the aquarium and don't generally cause problems. Strains that have caused disease have been "selected" by struggle with a fishes' immune system, so that the strain of commonplace bacteria in a compromised fish is the more virulent.