I have an albino tiger oscar that's about a year old. I've noticed his fins look thin and torn. My first thought was he must have fin rot. Here's where I am a little confused. He should be mostly white, but he is starting to develop some black. He has dark areas around his scales and he has a black spot near his tail. He also has dark spots at the base of all his fins.

I have 1 pleco, 2 barbs, and a black convict in the same tank. None of the other fish have any symptoms.

Any ideas of what my cause that?

The black areas may be damaged or dead tissue. I know with goldfish, after they are injured, they get black areas along the damaged fins. That indicates that the area is healing, and it's actually a good sign. Your oscar could have fin and tail rot which can be treated with aquarium salt and antibiotics, or maybe one of the other fish has been pestering him. What kind of barbs do you have? Some species may be nippy and could have bothered the oscar. Plecos are known to suck on goldfish, koi, etc. but I don't know about oscars. Convicts aren't exactly peace lovers all the time either. I would watch the tank for a while (both daytime and after dark) to see if you notice any interactions between the fish. Either way, you may still want to add aquarium salt (a tablespoon per 5 gallons) and some antibiotics to help the oscar's damaged fins. I mostly use Maracyn I by Mardel which is erythromycin.

I hope he gets better!