Verified answer

You can't have 2 of these fish in a 55 gallon anyway. Oscar will need at least a 75 to himself. Jacks and GT each need a 55 to themselves.

Oscars get too big for a 55 gallon aquarium anyways. They have trouble turning around in the standard 55g.

You can do a green terror and a jack dempsey, but make sure they are each about the same size.

You just did of a combination? Get out of here...