So...Those are good water parameters for Centrals.
Any of those combinations of species may work. But.... sajica get fairly large, and territorial, when I kept them as adults, I could only keep 1 pair of that species per tank, the alpha pair always put too much pressure on a subordinate pair, or other similar pan type cichlids by the time they hit the size of a soccer ball.
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Nicaraguans may be a better choice to try and keep with Oscura. being very different in appearance.
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6 Rainbow cichlids
1 Oscura
2-3 Macaws???