Well, last summer, I had ruby greens also, a breeding colony of 1-1.5 inches and I mixed them peacefully with aulonocara, but then my ruby green group was sold which I regret. Most of the times ruby greens are only aggressive to conspecifics. But I am not too sure if they should be mixed with rams. You can try, but the water conidtions wouldn't be correct. What size tank?