okay lets say few facts about my aquarium:
1.I feed them four times a week to full
(one day feeding time and then one day no feeding,that helps to keep them more healthy and active/fit)
with a big variety of foods such as river shrimps,hikari pellets,vegetables,blood worms,earth warms,snail,bugs,frozen fish's,catfish's pellets or pleco pellets and I only feed them with a feeders once a month!
2.I do 40-50% water changes every week
3.I'm using three external filters load with bio rings and ammonia remover
each filter has about 8-9 litres but when I move houses I will get 300 litres sump with no wet&dry,so I will have extra 300litres and all sump will be full up with biological filtration such as lava rock,bio rings,bio balls etc!
4.all my Oscars are TIGER Oscars! there is no red Oscar in this aquarium!
I got my first Oscar from a person that keep him in 10 gallon fish bowl,he was about 5-7cm and was feed with gold fish flakes

he came to health very quickly and now he is about 9-11 inch and eats everything!
my second Oscar is an tiger Oscar too and I bought him from my local fish shop about four months ago,he was about 3-4cm only but he grown very fast,now he is over 6-7inch
5.I don't add any chemicals to my water/my fish never been ill
6.my fish have a lots of hiding places and that helps to keep them feel safe.