I used to keep them. Had a Betta in a 20 gallon, and the I had a community 125 gallon tank. Back in the day, I had a 125 gallon African Cichlid tank, and I also had a 75 gallon with a lone Oscar in it. Loved that fish.
Here is the community 125. I had several types of catfish, but the corydoras eventually overwhelmed the tank with their breeding. This was before I started adding fish, while the tank was cycling. The centerpiece of this ended up being a green severum.
Here is Ickey, our betta. Wife is a Cincinnati Bengals fan, he had the colors, hence he was named after Ickey Woods.
And this was the best fish of all time. This is a 48" 75 gallon tank, so you can see how large he got. The tank is so sparse because that is all he would allow in there. He tore everything else up. His favorite thing was to swim around with a golf ball in his mouth. This is Melvyn. Oscars are truly wet dogs.