100% agree with spish here.. your being offered extremely good advice so for the fishes sake take it.. we see abused oscars all the time, its not pretty and in a few months when you would be "proudly" posting pics of yours all crammed in.. well ,no one is going to be in the slightest impressed,what im saying is that its easier to walk away from temptation that it is to get bagged for it later!!
( Bo the oscar in my sig, he was kept in cramped conditions before i go him, he has permanent fin damage from it- probably due to having to keep them raised to swim over other fish-he also behaves very oddly in the dark.. i assume that when the other fish in his cramped tank fought with him) but without sounding like a marter i dont spose many people wouldbe willing to take on a "2nd hand" grumpy abused 12 inch monster fish, with issues!! so think on! )