Fish rot issue

[squealor]

Three of my Serpae Tetras (the first batch of fish to be added to my tank 1 1/2 years ago) have developed fin rot. As soon as we noticed, we put them in a 5g quarantine tank. We first did a full dose of Maracyn. There was a bit of improvement, but not much. So, once that was done, we did TWO full rounds of Maracyn Two. That has just ended... One fish looks pretty good, one looks better, but not back to normal, and one is still missing quite a bit of her fins. Just a few questions:

1. Do I put the one that looks ok back in my main tank or will she spread the disease?

2. What do I do to save the other two??

They are my oldest fish, so there is quite a bond and I really don't want to lose them!

 

[Zagz]

I would put the good fish back in the main tank. The best treatment for fin rot is clean water. How often do you change the water in both the main tank and the QT? I would treat the other two with water changes and pima/melafix. Run activated carbon in the filter in the QT to remove the remainder of the Maracyn.

 

[squealor]

On the big tank, we do 50% pwc's weekly. On the QT, we do 75% pwc weekly. I'm not sure a 5g hex has a spot to put activated carbon in it... but I'll take a look when I get home.