i have 3 oscars with 2 motoro's, but it's only been about a month and i plan to ditch the oscars soon. the oscars pay no attn to the rays and vise versa, but i wouldnt call it a sucess because of the short time theyve been together and the fact that im going through massive amounts of food just to get the rays fed, and massive amounts of water to keep the tank in check.
can it be done? depends on the individual fish's temperments, but even if it works for a month, year, etc.. there's no guarantee and i would expect bad things in the future.