Eh, is it a 20 long? I know they prefer longer tanks, it should be fine in one of those for quite a while, once it gets to full size put it back and it should do fine against the parents. Mine is w/ a gymno balzani, heckelli threadfins, a butterfly fish ( i prefer black wolf aro), an albino senegal and a regular senegal. All in a 30 ga growout. But none of the fish are over 3.5 inches as of now are your parrots larger?
Also do you have any plants in the tank? Ctens love plants, thick stuff where they can get into and hide. If you add enough of that it should be able to evade and hide from the parrots enough to not really be affected. Mine is actually kind of bully-ish. He comes in hot like hes gonna nip or ram and then slows down and looks like a leaf and drifts away. Pretty funny haha
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