I see in your signature that you have 6 angelfish in your 55 gallon tank. Does every one of them have finrot? Are they adult angels? If they're adult angels, 6 of them will probably be too many (and too large) to keep in a 20 gallon tank. BUT, if that 20 gallon tank is cycled and able to support 6 adult angels, you definitely should put them in there and treat them (before other fish in your 55 gallon tank get infected with finrot). Just make sure that the pH and temperature of the 20 gallon tank are the same (or at least very similar) to those of the 55 gallon tank, so that the angels don't get any pH and temperature shock upon the transfer. Also check nitrate in both tanks - if it is much higher in the 55 gallon tank, do a water change to lower it so that it is the same (or similar) to that of the 20 gallon tank.
As for the medication treating finrot, you'll have to ask someone who knows about the medications - I don't have any experience with fish medications, and I wouldn't want to give you some misleading advice. I am sure your fish store has some medication for finrot though.
Now, just because you haven't started treating the angels yet, does not mean you can't perform frequent and large water changes. If your fish are sick, water changes are always good to perform. I don't know how helpful aquarium salt is with finrot but I hear that salt is generally a good treatment for any fish disease. So you could add 1 tablespoon of salt per 5 gallons of water to the tank in which you'll treat the angels. (Dissolve the salt first in a cup or two of tank water, and then slowly and gradually pour the solution into your tank.)
Thanks Isabelle, One of the angels is an adult size the others are babies yet and only like nickel to quarter size. The othe fish are ok, just the angels seem to get this, the tetras never get it. I don't know why but that is how it goes. I have melafix to treat the fin rot and it seems to do well. I will try this and see how it goes.
Water changes are always your first line of defense when an illness shows up. I personally wouldn't add salt to a freshwater tank.
The angels may be getting their fins nipped and that's why they are the only ones getting fin rot or not. Sometimes it just shows up and fish with long fins are the ones hit first. Maracyn and Maracyn II are good for fin rot. If the 20G is cycled then it would be a good idea to move them and treat them there, it will use less medication also.
Sorry for the salt advice if it is not safe for angels. I just generally read that it's a good treatment for various freshwater diseases, so I thought maybe it could help. Angelfish are not scale-less fish, so aquarium salt (when added in appropriate amounts) should not hurt them. I have heard (don't know if it's true) that only freshwater tanks with scale-less fish should not use aquarium salt in case of a disease. After the treatment is complete, the salt can quickly be removed from a tank by frequent and large water changes.
Carol, did you perhaps mean that aquarium salt is not safe for freshwater angelfish? Or perhaps for a freshwater tank containing live plants? Or maybe for a freshwater tank that has both sick and healthy fish, in which case the healthy fish wouldn't take the salt well? How about aquarium salt used on sick freshwater fish (with scales) in a quarantine tank?
According to David E. Boruchowitz, in "The Simple Guide to Freshwater Aquariums":
"Salt is a wonderful treatment for wounds, infections, and parasites. It stimulates the fish's production of natural protective slime, and it deters or kills many disease organisms. This doesn't mean you should start adding salt to your tank whenever your fish don't look right! If they have cottony white growths on them or open, gaping wounds, or creatures hanging from them, sucking their lifeblood, salt is a good remedy."
If salt was to be added they would have to be moved to the 20 gallon mentioned, because her signature says the 55 gallon also contains three peppered cories, they would not appreciate salt.
Ive always heard salt was a good way to speed up the healing process in fish and am curious as to why butterfly shoots down this approach.(Not that I doubt you, you are most definitely far more knowledgeable about fish than myself, just curious. ;P)
There are many good books that recommend salt as a treatment for various illness and I didn't mean to be abrupt or "shoot down" the salt recommendation.
I was just expressing an opinion, every time I have used salt I've had bad luck so that's why I recommend water changes instead and Maracyn, Maracyn II. Salt stimulates the slime coat and sometimes that extra slime can cover up parasites and other nasties thus protecting the nasties from treatment.
So that being said, many different people treat their fish for disease in many ways. And they work! I was just expressing something I feel strongly about
Isabella I have the same book!! It's an excellent book.
LOL Carol! I didn't even take it as you "shooting down" the salt recommendation I don't mind hearing various opinions, especially opinions from you, because I know how experienced you are and it is you that I have learned so much from.
So, SkippI and Badger, if Carol says so, do trust her. I've never gotten bad advice from Carol. Besides, I've never added salt to the tank with my angels while Carol HAS done so. And it's best to listen to someone with experience. My recommendation came from readings on Fish Lore, the Internet, and in books.
I'd still recommend salt, BUT it may work differently for every individual, for every fish species, and for a specific disease. There are really many factors involved.