Black moor, shredded tail

Question
We've had a black moor for five years now, and he's had illnesses on and off recently.  The latest was some tail rot that we treated with Melafix, which we're on our 7th day of dosage.  Around day 4 everything looked great, almost like the rot had stopped and the damage was gone. We wanted to finish the recommended treatment but now his tail is in shreds and there is a white line around his tail that separates the shredded part from the healthy part.  Don't know if it matters, but we introduced a baby black moor to the tank about 3 weeks ago.  Please help!  

Answer
Hi Rob
I used to recommend MelaFix for lots of things.  Then I was talking with someone, and they mentioned that MelaFix is really only good when adding a new fish type of stuff.  He said PimaFix was better for an actual disease treatment.  Apparantly it's good for a lot of gram negative diseases(which most fresh water bacterial infections are) and fungal infections.  So, I've started recommending that instead of the MelaFix, and also use that as opposed to the MelaFix.  So, I'll start with saying you can try the PimaFix instead.  

Also, how large is your tank?  With 2 goldfish, you'll want to have a minimum of 20 gallons, though 30 would be better.  If the tank is under 20 gallons, it may be that the new fish added extra bioload on the tank, and the beneficial bacteria can't keep up with the added load.  So, my next question is, what's your water parameters-ammonia, nitrite, and nitrate?  Ammonia and nitrite should read 0 ppm, and nitrate under 20 ppm.  

Usually fin rot is caused by poor water conditions.  How often do you do water changes?  I usually will recommend changing 25% of the water once a week-unless the tank is overstocked more water needs to be changed or more frequent then once a week.  Do a water change, give the PimaFix a try, you could also add some aquarium salt, dose at 1 tablespoon per 5 US gallons-as long as there's no plants, snails/invertebrates, or salt sensitive fish like tetras or catfish/plecos.

Hope that helps and good luck!!  Let me know if you have more questions/problems!!

Christy