Oscar missing some of tail - dying

Question
I have an oscar approx 2 months old, it started with 2 holes in its tail exactly the same shape and size (tictac shape) these holes were not there when we bought him a few weeks ago. over a few days, the middle of his tail disappeared where the holes were, and now more than half his tail is missing. He looks like he is having difficulty swimming, and didnt eat for a couple of days. We clean the tank very regularly, and he is in the tank by himself. He was in a tank with another oscar when we bought him.
Do you know what this could be? Will his tail mend or could this permanently cause him damage affecting his life?
He is regularly floating in 1 spot or sitting on the bottom of the tank... what should I do?

Answer
Hi Phoebe,
  It is possible that his tail was damaged before you got him -- sometimes it takes a few days for the damage to show. If this was the case, then he would start healing after a few days and the tail damage would disappear. If the tail keeps getting worse, that indicates that there is some other, ongoing problem.  

  Do you do regular partial water changes?  

  You need to be changing at least 25% of his water, once a week, every week, to keep an oscar healthy.  

-- Ron
  rcoleman@cichlidresearch.com
  Cichlid Research Home Page <http://cichlidresearch.com>