Ok so I had a QT up and running for a while now and everything was fine I quarantined all my fish I made one mistake I bought 5 golden danios I wanted 6 but they only had 5 in my LFS left.They all went through QT with no problems I transferred them to my 36 gallon and everything was well until I noticed that one of the danios was bullying one of the others I had to separate this one in a separate container I wish I had noticed this earlier than I did because the bullied danio had one fin nipped and looked very thin unfortunately even with separation from the other the fish ended up dieing to which I felt very guilty. Now there are 4 and all are doing well. I also lost a melanistius cory which also went through QT. Oddly there was some sort of growth on the fish when it was in QT at first I thought it was fungus so I treated the fish with Tetra fungus guard which seemed to help and I left the fish in QT for one more month to make sure the disease was cured & all went well. What was strange was that the others were not affected. Two weeks after transfer into my 36 gallon I notice the growth is back and none of my other cories nor the other fish are or have been affected but this cory died. I know it's not columnaris because that would have reared it's ugly face and affected the fish by now. My question is since I have already broken down my 10 gallon QT before this happened since I thought all was going well I want to replace the cory and also try to put atleast 2 more golden danios in my main tank but know I have to QT first. I have an empty 3 gallon that am not using I was thinking of using that because I just don't want to set up a big 10 gallon tank for QT for 3 fish. Do you think this is ok? Right now in my main tank I have other fish that are doing fine including 5 cories and the 4 danios. Any advise would be appreciated. I had the QT 10 gallon set up on my kitchen counter and my hubby was happy to see I was finally breaking it down although he understood why I had to QT the fish but it took more than 4 months to do it since I was restocking my main tank with some new fish but if I have to QT 3 more I am hoping the smaller tank would work and I know I will have to do water changes.