Can Jack Dempsey Live With Oscar?

Both are large, food driven cichlids that hobbyists commonly keep together, and the size works out reasonably: the oscar's own profile allows tankmates as long as they are too large to read as prey, and a 20 cm Jack Dempsey clears that bar comfortably. The Jack Dempsey brings its own caveat, since even a bonded pair stays hostile to other cichlids, so this is a fish that tolerates company rather than welcomes it.

20 to 28 °C is shared by both, though the working range narrows to pH 6.5 to 7.5 once the Jack Dempsey's slightly harder preference is accounted for.

This is not a tank for a young pair growing up together: raise them at a comparable size, use the oscar's own 540 litre minimum or more so nobody is cornered, and add plenty of driftwood and rockwork to break sightlines into separate territories. Watch feeding time particularly closely, since both fish compete hard for the same meaty foods, and a subordinate fish that stops eating at the table needs moving out.