So I have a guppie that is a lower sword tail and his back fin is going away it does not look like it has white around the edge of the tail so I’m not sure if it’s fin rot or not. I have 5 other guppies in the thank that has no obvious problems with their fins. I want to know how I can help the little guy. I set up my tank 6 weeks ago and is finally getting to a cycled tank. I do not have the means to do a hospital tank so I don’t have a separate tank to put him in to treat. Over the past 6 weeks I have had a small ammonia problem and has never had it down to .00 ppm. Right now with a API liquid test kit and it’s at .25 ppm but when I test it at PetSmart they say it’s .00 ppm. So during that 6 weeks I have done water changes every other day using prime and safe start plus to help during the cycling period so the level don’t spike. I don’t necessarily want to treat the whole tank for just the one fish but I have no other options right now and I want to help him. I know my tank is clean and the levels are good. I don’t know why he has gotten to this point. What can I do to help him? I also heard that if I do treat the tank I have to take out the carbon filter. If I do that for the 7 day treatment, won’t that mess up the cycle and make the ammonia and nitrites rise? I don’t think the ADF and other fish are bitting his tail because I have never seen them attack his tail but even if they did how can I help him get it back? Please help!!