Two Oscars in a 30 gal. Bad idea. I had 2 Oscars in a 55 Tempered glass . They got into a fight and shattered the 55 what a mess. Most Oscars do not get along in a aquarium setting even if they grow up together. You almost always get a dominant one that will try and kill the other ones,even in very lg. tanks. There is always an exception. I have 3 lg Oscars in my pond along with 4 15in plectos,5ex lg. pink kissers,2 redlg.parrots, 3 ex lg.bala sharks. loads of apana wood,and water hyathens. they still face off with each other but no damage. they always end up backing off after there display. When they were in a tank there was a constant battle. 1 Oscar in a 55 is a load. If you don't separate them the fish will surely die.