My 55

you have to be a user to see the pictures. I hate to say this, but if its a tiger oscar you're going to need a larger tank(if you want it to live a happy/healthy life) when it gets bigger than 8-9" and thats even pushing it. I hope for you its not an oscar, but it probbably is
 
I havent personally had one, but here's a good site on them, seem like they are MEAN as hell once they pass the 5-6" mark. And in my opinion, you will probbably need a bigger tank in the future, because they can hit 12-14" and 55g's are only 12" deep so it will have a VERY hard time turning around. Not to mention they are prone to hole in the head disease like oscars, most likely because they are VERY messy for their size and you have to really keep up on the water changes!! Good luck, they look fun!!


Here's the site with info
 
AquariaCentral.com