I just bought some Keyhole cichlids

And so far they are awesome in my 55 with 2 Blue Acara "Aquidens Pulcher" And a female Con.. I am how ever going to feed the female Con to mY P-bass, and the Blues are already spoken for
I would have suggested a couple maybe two angels and 3 to 5 Keyholes and a pictus or a couple other small cats like corys
Which still might be a little overstocked but hey these species would give you a lot of fullfillment in that size of a tank
I did raise my Oscar in a 40 for 3 years

and i'll tell you i looked in every place i could to hear what
I Wanted to hear

and kept hearing it at the pet store

But when it comes down to it, An oscar can grow to a foot in less than 18 months given the right situation, and given even just adiquate conditions at least eight inches

And let me tell you in that tank it wasn't fun anymore

But thats where the motivation came in

And i was born with dirt in my mouth and the snakes fart blowin dust in my eyes so the ghetto stuff was a dream to me "lucky you "

We lived in a dirt lot between Projects LOL.. Now i have big tanks
A jack does not grow as fast but would do better with a mate

And then it would be suggested to go with a 55 and if any tank mates it would be best if it were a pair of cons or Firemouths

As they can hold their own to a point with Jacks
More solitary monsters to keep are ones that do not swim much. Ones that just kinda sit

I see people with Wolves in smaller tanks.. Don't know much but it looks good

Or maybe a Goby

A larger one "like the Water cow.. Or Sleeper or Marbled. .. They just sit around most of the time

And they are MONSTERS..