One day about 7-10 days ago I woke up and found one of my tiger barbs just lying on the bottom of the tank without any warnings signs the day before. It was eating, looked normal, and was swimming with the other barbs. I took it out and put it in a QT tank with a few caves thinking it would be dead within the day. Its been over a week with a few water changes and its still alive. It's still on the bottom though and keeps trying to swim. I've given it a little food, but have not seen it eat any. I added some Prazipro, but it doesn't seem to have had any effect. All of the other fish in the tank are doing fine. The fish still looks normal: no bloating, disheveled scales, ulcers, or signs of attack. Any ideas what is wrong or if there is any hope for recovery?