I wouldn't recommend that bicher with that ray at all i had a retic in with a bicher and the bicher first ate his disk and then his eyes all within 8 hours while i was at work. I dont think that datnoid will do much to him their kinda shy in my experience to be safe let the ray grow a little.
i have 2 10" ornates and a 6" motoro and they always chill out together. never had any problems thus far.
The datnoid could be a bit of a bully towards the ray but should be ok too.
I have a 14" P. Endlicheri with my 6" Diameter Male Motoro and it goes very very well. The main rule of keeping bichirs with a ray is dont starve your bichirs....