in need of fish suggestion

Oscars get way bigger than twelve inches, I still think the combo of an oscar and JD is okay just filter the pejesus out of the tank. I have Oscar JD Blackbelt in a 90 with no problems (same footprint as a 75 a little more swimming room though). Other ideas are texas (carpintis) or motaguense maybe, might kill the JD though. Salvini and green terror were also good suggestions. How about geophagus brasiliensis or a red head earth eater?
 
thanks for all the advice, I got my oscar yesterday

the tank now has
1x3" JD
1x1.5" Oscar
3x2.5" Giant Danios

I might move the other 2 Giant Danios back into the 75, they're a little too big and anbnoying in the 20H

I might get some zebras for the 20H

do you think I'll be able to keep some more community based fish in the 75, perhaps some tetras
 
Tetras will end up fish food. Make sure and up your filtration, you should be moving 750 gph plus. The oscar will eat about anything that will fit in its mouth.
 
AquariaCentral.com