How to tone down Oscar territorial aggression?

Go to VIP petstore, they are selling backup air pumps that can run for 6 hours on full power and way more on half power.I've got two oscars in a 310litre tank with 2 plecos. The female Oscar is 34cm big and the male 28cm. Oscars tend to fight if they want to breed(male and female) and they will fight for their territory. If any other fish come close to their breeding spot, they will try to kill and fight for their territory. W hen you do a water change and your water is between 26 and 28 they want to breed and are very aggressive towards any other fish. It is relatively easy to sex oscars and that is how I got my male and female together. Once they team up, they are going to be aggressive towards other fish. If any oscars doesn't team up you might end up with two males or two females in a tank, then the fights is going to be bad. At 27 deg two male oscars will fight for territory. In a small tank one might end up dead.Sex your oscars and then you will know what is going to happen. The only oscars I can not sex is the oscars with their long fins. My oscars if tame and you can scratch their heads and play with them, but be warned that is they want to breed, they will bite and rip. You wound even be able to do a water change.