I would give it a salt bath...make sure the salt does not have iodine in it. There is info on caudata culture on how to do a salt bath. However, if you want the quick version what I do is take a small container and put new dechlorinated cold water in it and shake the salt in it like you were salting food - just a thin later on the bottom, stir it in until it desolves, then put the paddletail in for 5 minutes. Then even if the white is still there put it back in the hospital tank and watch it. Repeat this every day until the white is gone. Are there other paddletails in it's normal tank? Is it a new acquisition?
In my experience if it is just a surface infection from it being in a fight or getting hurt on something in the tank than this should clear it up in one or two treatments. However if you have just gotten the newt then it may be a sign of some internal sickness which would mean that it does not heal up quickly and you may need other kinds of treatments.
Hope that helps.
