I've got five fancy guppies in a 12 gallon tank (my goldies' old tank). I've had them about a month now and suddenly they aren't looking so good. Water temp 78 degrees, pH 7.4, Ammonia 0, Nitrite 0, Nitrate 10, Prime water conditioner, salt. I change 30% water weekly and test it weekly as well. I feed them a variety of different tropical flake foods. One of the guppies' tail fin suddenly looks all bunched up, whereas before it was all spread out, and it's gotten darker. Another one looks like it may have the beginnings of fin rot or something eating away at its tail. They're still active little guys, still eating. What kind of fin rot readily eats away at the fin within a couple of days? I initinally had 6 guppies but one died and appeared to have suffered through a really really bad case of fin rot. I had treated with Maracyn but to no avail. I hope none of the others still have it. Arghh.

Sorry to hear about your fish.

I am extremely new to tropicals but I had GF before this. You might try Maracyn-2 or try them at the same time, as one is gram negative and one is gram positive. What one doesn't cure the other might. I have had great sucess with my Goldies using Maracyn and Maracyn-2. Another option could be Tetracycline, but I have never used this, so I would recommend that there is no Maracyn in left in the tank water before using it. Also, if you have a quarentine tank, I would recommend using it for treatmet if you haven't already.

You could always try a salt dip/bath, as this is a safe way to treat a lot of ailments, but you shouldn't use other treatmetns at the same time. I copies this from a website a long time ago, soI don't know where but this is how you do it if your not sure:
"Days 1 - 3: add I teaspoon of salt per gallon of water, every morning and every night. (2 teaspoons /gallon/day)
Days 4 - 7: Leave water alone.
Days 8 - 10: Remove half of the tank water each day and replace with unsalted, chlorine-free water at the correct temperature.
If by day 7 you see any improvement (but not a total cure), wait until day 10 to start changing the water in the tank. Be sure to change half the water once a day, for three days at the end of the salt treatment. Also, don't wait longer than 10 days to start changing the water, as the salt itself can begin to cause problems for your fish."
You may also try "Add salt at the rate of 1 teaspoon per gallon; if you normally add salt, double the amount you usually use".

If the darker parts of the tail are only is spots or sections, this could be an ammonium burn. I have had ammonium spikes I never detected until I saw the burns. The burns are a sign of healing and will go away over a few weeks, and are nothing to worry about.

I don't know if I have helped at all, but I hope I have. I'll keep my fingers crossed for your fish as well as that someone will come along who knows more than me. Good Luck.

Thanks, Sunnygirl! Lukcily, the little guy perked right back up the next day and they're all doing pretty good now. I'm medicating with Maracyn-2 and I can see some growth on his fins so I think they're going to make it Yay!

Always isolate a sick fish, especially when medicating.
These medications can be bad for the other fish when they're healthy.

Could it be possible that somebody got nippy?

Chrissy