Are you trolling here or having an off topic argument as this doesn't make sense to me, the filter supports the tank not the other way around, the bacteria supports the tank too.
An 8inch ray is fine in a 250 but it may not live there forever if the 8 inch ray is a well fed female motoro as she will outgrow it but if it is a small histrix variety male then maybe yes. As per my previous question that you did not answer, what species of ray are you talking about.