how would u cut down on the waste of an oscar
Sorry, how 'bout if your not fed for a week, you'll poop less, but you won't be very happy about it. I wouldn't get an oscar. You're tank is just not big enough, and if you're having problems with your filtration as you mentioned in your other threads, it won't work.
Just keep with what you have, the angels and the BN, right? That's a great tank right there. Oscars are cool, but I really compare having them to having a dog. It's very nearly that much responsibility. The people I know that have them dote on them like they're little children. Its really a special mentality to have that kind of fish. I don't keep that kind, I like the smaller, schooling fish. I kept a two goldfish for five years in a 45g, and they were super messy and taking care of them was a pain in the rear! But they were like dogs or cats to me, very much part of the family, and when they died, it was a significant loss.
I'm not trying to discourage you, I just think that caring for an oscar, in the long, long run, is a big effort. You really have to be prepared to invest a lot of time and money on filter and tank upgrades. That is certainly beyond most people's budget.
Enjoy what you have.