I keep indo tigers up to 11 inch with my motoro and retic. Added rays about 10 weeks ago.
They are great tank mates. Dats never pick on the rays which are 6 inch disc.
Tigers have a very powerful snap when they engulf their food, so I have been keeping an eye during feeding, throwing food in left, middle and right side of tank, so the rays less likely to get in the way of the tigers diving for food on tank bottom.