goldfish fin rot

Question
Hi, I have a 6 gallon fresh tank with 2 goldfish and one alge eater.  
My black goldfish has fin rot, I just noticed this morning.  
I read about melafix, but here is my question...

Should I remove the sick fish and treat her in a separate Bowl?  Can I use a
glass bowl? I don't have another tank?
If I can and should treat her in the existing tank, should I change all the water
and than treat it, or leave the water as is treat, and when she is all better than
change the water.

If I am to separate her (not sure why I say her, maybe because her name is
kathleen) and she is used to a tank with a filter, will it be bad to have her with
no filter??
I have had this tank for about 4 months, and have changed 30-50% of the
water every other week or so, and the water has been nice and clear, before I
even realized there was a problem with her today, I planned on cleaning the
entire tank and changing all the water... Thoughts??

Answer
Hi Robin,
Melafix is generally used only to heal wounds.  Even though this will help, it will not kill the bacteria that is causing the fin rot.  There are 2 meds called Maracyn and Maracyn Plus, one is for gram positive and another is for gram negative.  We dont know which one it is so people often dose both meds.  Or you can use any antibiotic treatment such as chloromycetin or tetracycline.  Soak some of the fish food into the antibiotic medication and let her eat it.  Sometimes the fish will taste it and spit it out, so what I myself sometimes do is, not feed the fish for 1-3 days to make they hungry then feed them the medicated food.  Water changes must be done to keep water quality at good levels.  Good quality water encourages less stress and healing.  You have to treat both the fish and the tank, if you choose t seperate her from the main tank then you would have to treat both tanks.  The choice is yours.
Good luck with her.
-Matt-