Alex as with the above smaller fish will be a meal, but my O now Has 4 angels living with him, added after he reached the 10inch mark and they get along fine. As said though it depends on the individual temperament of the O. Murphy likes to shoal now and again with the rainbows & is generally quite gentle. But you could end up with a right demon

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If you went O's and angels, I'd recommend getting the angels first and add a juve Oscar soon after, if they grow up together they'll get on better.