sick comet fish

Question
QUESTION: Hi Krissy, my comet fish has been suffering from fin rot for a few months now, her veins on her tail are red plus her tail is torn and the edges are black in spots and white in other areas. Plus she has had secondary infections of cottony growths. I have tried so many different medications over the months that haven't worked. A few weeks ago she was at her worst, sitting on the bottom of the tank and quivering, I think the infection must have been effecting her internal organs. I asked another expert (her account is now deactivated) who recommended Maracyn, but unfortunately we cannot buy that here in Australia - so I used some Aquari-cycline (tetracycline) for 7 days instead which seemed to help her a lot. She started moving about and eating again but the fin-rot still seems to be there - about half of her tail has disappeared now! I have been constantly using Melafix and Pimafix for the last few months to try to fix this. A few days ago she again started sitting on the bottom and quivering so I have started administering tetracycline again. Her condition has improved once again but I know that as soon as the 7 day treatment is finished she will probably go downhill. I just can't get rid of this infection! Soon she will have no tail left at all. I hope you can help me?

Thanks
Jayne

ANSWER: I will do my best to help you :) I need a little more information first though. What are your water levels and how often do you change water? The Tetracycline worked before, or at least started to. At the end of the seven days, I would do a water change, changing as much of the water as I could get out of the  tank and treat again. If the condition continues to get better between now and then with no relapse, great. If at any point... it starts to regress or change in a negative way OR as you near the end of the second treatment there is still significant signs of infection, let me know. Include the following information with your message...

Water Levels (pH, Nitrate, Nitrite, etc)
All species of fish in tank
Water changing schedule

In the meantime, I'll do some research to see what else I can find out for you. It would actually be helpful if you could send the above information to me now, then again with new readings if you have more problems down the line :)

---------- FOLLOW-UP ----------

QUESTION: Thanks Krissy - I will follow your advice with the tetracycline for now. I'm not sure of the water levels in my tank; I've had it tested several times at the local pet shop and they said that it is perfect (although I think that was definitely poor water quality that caused the original sickness).

The comet is the only fish in my 15 litre hospital tank, as I took her out of the tank with the other goldfish fish about a month ago. Generally I change 25% of the water every week, but since using the tetracycline I have been doing this every 2 or 3 days as the medication makes a HUGE mess of the tank. I hope this information helps...

Thank you so much for your help and for such a fast response!
Jayne

Answer
I'm still researching options for you in case this doesn't work. I was wondering, what type of water conditioner you are using? I recommend Aquarium Pharmaceuticals water conditioner with the healing power of aloe. I'm not sure you can get it there, but if not and you aren't using a similar product already look for some that has the ability to heal damaged tissue. It will help those fins and tails get healthy again :)
Again, if the tetracycline isn't working, drop me a line. I'll keep researching and come up with some other options just in case :)