Ok I'm not to sure how this site works but I joined in hope to find some answers for my fish... I have a 115 gallon tank containing, 2 large red Oscars (10 & 7 inches) , albino Oscar (6 inches), 4 jack Dempsey ( two are 6 inches & two are 3 inches) , convict ( 3 inches) , angelfish (4 inches) an 2 Plecos that are 8 inches... all the fish have been together for a long time an for the most part get along they all have their own special place in the tank to call their own.. expect 1 of my Plecos recently purchased at petco as an adoption. He has been in the tank for 6 days. 2 days ago I noticed a hole in his back fin the width of a pencil I didn't think much of it because he's new an thought I may have missed that feature to him, however now his back fin and tail look torn an feathered. He is not picked on the other fish just swim around the plecos.. I'm thinking I bought him with Fin rot... An I'm not sure how to go about treating him.... Any suggestions would be greatly appreciated... Thanks in advance.